STUDIES ON ASPLANCHNIA EBBESBORNII. 



197 



FIG. i. Represents the reproductive system of a male-producing female, which 

 shows the presence of both male embryos and resting eggs. Where male embryos 

 and resting eggs alternate, the yolk is formed at intervals just preceding the growth 

 of the resting eggs. The figure shows the passage of yolk into the forming resting 

 egg- 



FIG. 2. Represents the reproductive system of a male-producing female, 

 which contains male embryos in different stages of development. The vitellarium 

 is free from yolk and shows the passage of cytoplasmic granules into the forming 

 male egg. One of the male embryos shows the condition at time of birth. 



FIG. 3. A mature double-shelled resting egg, which is filled with considerable 

 yolk. 



FIG. 4. A mature single-shelled resting egg, which contains less yolk than the 

 preceding. Its development is completed within the uterus and hatches imme- 

 diately after deposition. 



FIG. 5. A mature parthenogenetic female egg, which is entirely free from yolk. 

 A single polar body is formed. 



FIG. 6. A mature parthenogenetic male egg, which has the same structure as 

 preceding. Two polar bodies are formed. All of the above eggs show the presence 

 of a well-formed vitelline membrane. 



