84 EDWARD DRANE CRABB. 



make it easy to find the enclosed conoid sperm heads and to follow 

 the course of their tails (Figs. 2-5). 



D. Changes in the Oocyte Following Insemination. 



Whether or not there is a volumetric change following insemina- 

 tion in L. s. apprcssa eggs, such as has been found in the case of 

 the brook lamprey (Okkelberg, '14) and in the echinoderms 

 Arbacia and Asterias (Glaser, '14) and Asterina (Snyder, '25), 

 is not evident. However, ova were found which appear to in- 

 dicate such a change. The sections of the smallest of these ab- 

 normal ova, from near the anterior end of the hermaphrodite duct, 

 were about one fourth the diameter and number of those of in- 

 dividual ripe ovarian and recently " ovulated " ova. 



E. Formation of tJie Sperm Amphiaster. 



The early sperm aster occurs only in ova which have not under- 

 gone the first maturation division, and may be readily recognized 

 by its great size, which nearly equals that of the early egg asters. 

 This primitive sperm aster, or archiaster, is characterized by hav- 

 ing long stout rays and indifferently formed centrosomes (Figs. 

 u, 13, 15, 16). Perhaps these should be considered as unusual 

 centrospheres instead of centrosomes. It is apparent that the 

 sperm archiaster normally undergoes a sort of metamorphosis 

 before it forms a typical amphiaster. During this period of 

 change there is a marked reduction in the length of the rays and 

 a great condensation of the chromophilic substance in the centro- 

 some. The modus operandi of this metamorphosis is obscured by 

 the large number of polymorphic basophilik yolk granules which 

 retain the stain as readily as the centrosomes themselves. My 

 material indicates that during the prophases of the first maturation 

 division of the oocyte, these sperm archiasters reach their maxi- 

 mum size and subsequently the typical aster reforms from the 

 granules of the disintegrated centrosome of the archiaster and 

 reappears as a very small aster having short delicate rays and a 

 very condensed deep-staining centrosome. The amphiaster most 

 commonly arises from this aster (Fig. 23), about the time of the 

 first maturation of the egg (Fig. 20-25) but ma y arise earlier 

 (Figs. 19, 21). 



