BREEDING HABITS OF DESMOGNATHUS FUSCA. 1 9 



reported was continued under observation in the laboratory for 

 nearly a year. She was fed abundantly upon Drosophila, which, 

 as a "by-product" of genetics experimentation, has proved a 

 valuable laboratory food for adult salamanders. In spite of her 

 well-nourished condition, however, she gave no evidence of the 

 ripening of a new lot of eggs during the following spring and 

 summer, while another female of about the same size (87 mm. 

 in total length), which had not been gravid the previous year, 

 developed under the same care and feeding, large eggs which 

 could be conspicuously seen through the body wall early in the 

 spring. These observations are too limited in number to base 

 any definite conclusions upon them, but they at least suggest 

 that the females of this species do not necessarily produce eggs 

 every year. This hypothesis would also explain the fact that 

 I have found that occasionally females collected in early spring 

 contain no large eggs. The number of offspring in' this species 

 is in any case very limited, as shown by the small number of 

 eggs in a batch. These average about 20 in the cases which have 

 come under my observation in western Massachusetts, while the 

 largest number of ripe eggs which I have counted in the ovaries 

 of a single individual is only 28, and the number in a batch may 

 run as low as 14. If in addition to this characteristically small 

 number of eggs produced at a time, the females sometimes fail to 

 produce eggs every year, there would be a still further limitation 

 in the number of offspring. Such a reduction has been made 

 possible only by the high percentage of success in the develop- 

 ment of the few eggs which are produced. One of the conditions 

 contributing largely to this success is the large amount of yolk 

 present in the egg, which makes possible the attainment of a 

 considerable size and maturity at the time of hatching in conse- 

 quence of which the larvae are better able to take care of them- 

 selves. A second condition insuring the success of the offspring 

 is seen in the internal fertilization which insures the impregnation 

 and development of every egg which is deposited. In fact, my 

 experiments have shown that gravid females which are isolated 

 from the males early in the spring and thus fail to become 

 fertilized, do not deposit their eggs at all, and that by the middle 

 of August the eggs are already undergoing rapid resorption. 



