Ookinesis in Cerebratulus Lacteus. 395 



B. Observations on the abnormal eggs of Cerebratulus lacteus: 



(17) In CaClo eggs the chromosomes arise in the germinal 



vesicle in the form of thin threads. 



(18) In unfertilized MgClg eggs a protuberance is sometimes 



formed at the animal pole, as the maturation figure 

 retreats toward the centre of the egg. 

 (10) In unfertilized KCl -|- CaCP eggs the polocytes may be 

 formed ; the number and size of them vary a great deal. 



C. Observations of other forms : 



(20) In the blastomeres of the Avhite fish {Coregoniis albu^) 



rays are found around the karyomeres. 



(21) In the egg of PediceUina americana the spindle of the 



first cleavage mitosis is bent at the telophase toward the 

 animal pole (Dr. Dublin's observation). 



D. General conclusions: 



(1) The nuclear fluid is similar to hyaloplasm. 



(2) The nuclear fluid is usually neither alveolar nor reticular 



but homogeneous. 



(3) Diminution of chromatin (basichromatiu) does not take 



place at the dissolution of the germinal vesicle. 



(4) The centrosome is not a permanent organ, but is a tem- 



porary accumulation of centroplasm around the cen- 

 triole. 



(5) The centriolc is a centre for the formation of rays. 



(6) The size of the centrosome is proportional to that of the 



cell. 



(7) The middle piece of the spermatozoon contains a centriole. 



The spermatozoon, therefore, carries a centriole into the 

 egg at fertilization. The sperm centriole is not that of 

 the cytasters produced by the egg. 



(8) The cleavage centrioles are not new formations but those of 



sperm aster. 



(9) The position of tlie division centrioles is determined by the 



egg-organization. 



