130 George Lefevre 



cells arise, according to Torrey, early in the cleavage, and, wander- 

 ing into the blastoccel, are seen lying on the cells of the entoblast 

 into which they soon sink (Figs. 40, 41, re). Here they become 

 quickly absorbed and disappear. As long as they are present 

 they may be easily recognized by their small size and the con- 

 tracted condition of their chromatin. In Fig. 40 is also seen a 

 small cell pb, which is probably a polar body that has passed into 

 the cleavage cavity; its cytoplasm has a faintly radiate appearance 

 suggesting mitotic activity. 



6 Abnorynal Maturation Phenomena 



In an earlier part of this paper it has been stated that in some 

 instances the unfertilized eggs of Thalassema, after an exposure 

 to acid solutions, failed to extrude the second polar body, and in 

 still other cases that neither body was formed. It was frequently 

 observed, however, that such eggs segment and produce embryos 

 and larvae indistinguishable from those arising from eggs that have 

 thrown off both polar bodies. These abnormalities were not 

 associated with special solutions or external conditions of the 

 experiment, but they appeared at any time, and even with the 

 optimum solutions. 



It was of importance to determine the internal phenomena 

 present in eggs showing these abnormalities of maturation, and 

 an examination of sections from material preserved when the 

 unusual conditions were met with has brought to light several 

 interesting facts. In many of these cases, it is undoubtedly true 

 that either the first or the second polar mitosis, or possibly both in 

 some instances, may take place entirely inside the egg and without 

 accompanying cytoplasmic cleavage, and in this submerged con- 

 dition give rise to resting nuclei.^ 



a Absence of the Second Polar Body 



In the eggs which extrude only the first polar body, the second 

 spindle fails to assume its usual position, and instead of rotating 

 in such a way as to bring one pole to the surface, it sinks down 



^ Cf. the observations of King ('06) on the retention of one or both polar bodies in unfertilized 

 starfish eggs after compression. 



