Charles R. Stockard

The artificial production of a single median cyclopean eye in the fish embryo by means of sea water solutions of magnesium chlorid

While studying the influence of salt solutions on the development of FundM~s hete~vclitus it was found that one eyed monsters could be produced if the eggs were subjected to the action of MgC12 in sea water. This observation is of especial interest from several standpoints. It goes to show that salt solutions may induce certain effects through their chemical action rather than by the osmotic pressure which they exert. This view is now very generally accepted although BATAILLON 1) recently attempted to prove that the effects caused by the action of solutions upon eggs were due to the osmotic pressure of the solutions, since as he asserts isotonic solutions produce identical abnormalities. Such a conclusion can not, however~ be maintained since solutions isotonic with the MgC12 used in these experiments failed to cause the formation of one eyed embryos; and of the many chemical solutions employed no other seemed capable of inducing this effect. The structure and size of the lens in this Cyelopean eye is instructive in view of the recent experimental work carried out to determine the inter-relationship between the development of the lens and the optic vesicle.

A Further Analysis of the Hereditary Transmission of Degeneracy and Deformities by the Descendants of Alcoholized Mammals. II

Table II gives the relationship between the size of the litters and the mortality of the descendants from different combinations. It brings out in a way the variable internal and external factors to be considered in interpreting the conditions of the members of the numerous litters of animals. The external factor considered in the table is one of nutrition or environment, depending upon the number of young developed in the uterus at any one time. The table indicates the influence of an internal factor, the germ plasms concerned in mating related or non-related animals. Four combinations are considered: pairs of normal non-relatives, pairs of alcoholic nonrelatives, pairs of normal relatives, and pairs of alcoholic relatives. The first vertical column shows that in mating together normal non-related guinea pigs of the stocks used in these experiments the average litter contains 1.96 individuals. Fifty-one and eleven hundredths per cent. of the young were found in litters of two, and 20 per cent. of the animals occurred in litters of three. Fifteen and fifty-five hundredths per cent. of the animals were born in litters of only one young, and 13.33 per cent. in litters of four individuals. The next space below in the table shows the number and percentage of individuals living over three months 144

Effect of underfeeding on ovulation and the œstrous rhythm in guinea-pigs:

Under well-regulated food conditions the œstrous cycle in the guinea-pig is almost uniformly 16 to 17 days in duration. Underfeeding with a diet of 20 grams of carrots per day produces a prolongation of the diœstrum and, at the same time, a congestion in the ovary and uterus and a degeneration of developing graafian follicles. The extent of prolongation of the diœstrum depends upon the stage at which an animal is underfed. Underfeeding during the first 5 to 7 days of the diœstrum has only a slight effect, postponing the next œstrus for one or two days, while underfeeding during the later part of the diœstrum gives much more marked results. When an animal is underfed for 5 days, from the 12th to the 17th day after an ovulation and œstrus, the next ovulation and œstrus is delayed for about 7 days, being expressed at the 23d to 25th day instead of at the 17th. Should an animal be underfed for 7 days, from the 10th day to the 17th day after estrus, the next ovulation and estrus is postponed for 10 to 11 days, arriving at the 27th to 28th day, instead of the 17th day. This variation in the effect of the underfeeding when applied at different periods of the diaestrum is associated with the fact that the conditions of the ovary differ at the different times. Shortly after an ovulation the ovary contains almost entirely small primary follicles. These follicles are not so unfavorably affected by food conditions as are the large graafian follicles, which begin their growth and development during later stages of the dimstrum. A large follicle at the height of its development seems to require much better nutrition than a small primary follicle, and the lack of proper food arrests its progress very readily.

A Probable Explanation of Polyembryony in the Armadillo

By arresting the development of the fishs egg during early stages double individuals and twins are frequently induced. The interruption or arrest makes it possible for more than one potential growth point along the -germ-ring to give rise to an embryonic shield. In other words, accessory invaginations or blastopore formations occur as the initial structural step in doubleness. The interruption in the development of the fish embryo must be introduced during the cleavage stages and before gastrulation in order to produce such phenomena. Among hundreds of eggs arrested -during later developmental stages no double monsters or twins ever occurred. A complete account of these experiments is soon to be published but for our present purpose two facts are important: First, accessory embryo formations result from arrests in the developmental process; and second, the arrest must occur before gastrulation has taken place. In the light of these experiments it has seemed possible to interpret somewhat more clearly than has formerly been done the remarkable phenomenon of multiple embryo formation in the armadillo. On examining the uterus in two pregnant specimens of a South American armadillo von Jhering, in 1885, discovered that each contained eight fetuses enclosed within a single chorion. He correctly concluded that all of the fetuses in each mother had been derived from a single egg by some process of division into separate embryonic rudiments. After this valuable discovery .and interpretation, the, study of the armadillos development lapsed and nothing of importance was added for almost twenty-five years. Two series of investigations were then begUn simultaneously one on the Texas armadillo by Newman and Patterson,1 and the other on the South Americann species by Fer-

Experimental results bearing on the etiology of cystic growths in the ovary and uterus of the guinea pig

In experiments on underfeeding it was found that malnutrition readily gave rise to marked cystic conditions in the ovaries of healthy young guinea pigs. Such cystic conditions are, of course, frequently found in normal stock but here especially in old or unhealthy specimens. The changed nutritive conditions in the reproductive organs of underfed animals cause circulatory congestion, and as was pointed out in a previous communication 1 such conditions suppress the œstrous changes and prevent ovulation in these animals. The congestion and the high pressure resulting therefrom seem to favor the proliferation of the epithelial lining of the epididymal tubules located near one pole of the ovary, and the accumulation of fluid within the lumen of the blind tubules. The malnutrition expresses itself first within the ovary by a wholesale degeneration of developing follicles which seem to respond most delicately to changes in nutritive conditions. The congestion and follicular degeneration seem then to favor an overgrowth of the more resistant epididymal tubules which become distended and crowd out the parenchymatous portion of the ovary. Uterine cysts seem to develop in the same way as those above as a response to the congestion resulting from malnutrition. The open mouths of the uterine glands make their cystic condition rare so that among hundreds of ovarian cysts of all sizes we have observed only one perfectly typical case of uterine cyst. These experiments seem to indicate that ovarian and parovarian cysts represent growths of persistent embryonic tissue, and that an accompanying congestion and high pressure are necessary to the formation of typical cysts, and that these conditions may result from disturbed nutrition as is demonstrated by underfeeding the guinea pigs.