DEVELOPMENT OF PARACOPIDOSOMOPSIS 11 



in the anterior part of the egg" (p. 15). Silvestri also gives a 

 very clear description of the fate of the polar nucleus. 



In a paper published two years later, Silvestri ('08) described 

 the formation of the polar bodies in the egg of Ageniaspis. The 

 polar bodies are formed exactly as in the egg of Litomastix, 

 but their subsequent history is somewhat different. The three 

 masses of chromatin usually become reconstituted, each with a 

 reticulum and membrane, and all three lying more or less on 

 top of one another. In some eggs, however, the three polar 

 nuclei fuse to form a single mass, while in other eggs the second 

 polar body and the inner nucleus of the first polar body (or only 

 one of them) divide irregularly into parts, thus producing in 

 all some four or five nuclei. In the period between the third 

 and fourth cleavages, the polar nuclei lose their membranes, 

 and their chromatin becomes scattered in the form of minute 

 granules. This entire structure is now recognized as the para- 

 nucleus of Marchal, and the polar protoplasm siurounding the 

 embryonic cells in which it lies is his trophamnios. 



Martin ('14) has since reinvestigated the early development of 

 Ageniaspis, with the express purpose of studying the origin of 

 the paranucleus. He also finds that three polar bodies are formed, 

 but his account of their exact origin and position does not seem 

 to me to be entirely consistent. He states that the two chro- 

 matin masses which lie toward the center of the egg are both 

 derived from the first polar body, w^hile the third mass situated at 

 the extreme anterior end of the polar region is the second polar 

 bod5^ He bases his conclusion on certain stages in which the 

 second maturation division precedes that of the first polar body. 

 It is very difficult to understand how a chromatin mass, such as 

 that of the second polar body, could reach the position assigned 

 to it by Martin in his figure 16. Furthermore, he admits that 

 the time relation may be just the reverse of that seen in this 

 figure. I beheve it is practically certain that the three chroma- 

 tin masses shown in his figures 17 and 18 are incorrectly labeled. 

 In each figure I should interpret both the anterior and middle 

 masses as derivatives of the first polar body, and the posterior 

 mass, not the anterior, as the second polar body. As to the sub- 



