CONKLIN. 



[Vol. XIII. 



remains under the protection of the mother, i.e., by the sup- 

 pression of the larval type of development. 



Since the yolk is almost the only nutriment furnished the 

 young organisms by the mother, it follows that the sooner they 

 can begin to take care of themselves the less yolk will be 

 needed, while the longer they remain in the egg capsules the 

 more yolk will be required. While it is true, therefore, that 

 in the foetal type of development the number of germ cells 

 may be decreased, it is also true that the size of each ovum 

 must be increased. However, in C. convexa and C. adunca 

 the decrease in the number of eggs more than overbalances 

 their increase in volume, so that the total volume of eggs laid 

 is greatly reduced as compared with the other species. The 

 following table gives a basis for comparing the approximate 

 volume of the body of a mature female in each species with 

 the total volume of the eggs laid : 



Table IV. 

 Comparison of Volume of Adult with Volume of Eggs Laid. 



C. convexa, 



C. plana (dwarf), 



C. adunca, 



C. plana (type), 



C. fornicata. 



Relative 

 No. OF Eggs. 



17 



Relative 



Vol. of Single 



Egg. 



8* 



27|- 



50 



73 



Relative 



Total Vol. of 



Eggs Laid. 



I 



4i 

 IS 



Relative 



Vol. of Adult 



Female. 



4i 

 i3i 

 30 



The first series of measurements which I made showed a 

 close correspondence between the relative total volume of eggs 

 laid and the relative volume of the adult in these different spe- 

 cies. Later and more careful measurements have given the 

 results set down in the above table. The fact is that the sex- 

 ually mature females of a species vary so much in size, and the 

 eggs laid by them vary so greatly in number, that unless one 

 measures a very great number of individuals of all sizes, no 

 satisfactory ratio between the eggs laid and the volume of the 

 adult can be determined for a given species. However, all 

 measurements and enumerations show that the volume of eggs 



