2 24 BYRNES. [Vol. XVI. 



more indistinct, until finally the color distinction between 

 different structures is wholly lost. During the stage of the 

 archiamphiaster the chromatin of both the egg-nucleus and 

 the sperm-nucleus stains blue after corrosive sublimate acetic 

 (5 per cent). When the nuclei have attained their maximum 

 growth the chromatin stains ;r^ after corrosive sublimate acetic 

 (5 per cent). 



The only generalization that seems justifiable from the color 

 reactions in the o^g^ of Limax is that the different structures 

 in the cell periodically undergo chemical changes in their 

 constitution. Indeed, there is some evidence from the color 

 reactions that these changes in color may correspond to phases 

 of a cycle through which the protoplasm of the cell passes 

 during development. There is, however, no evidence for the 

 existence of an " archoplasm " which is distinct from the gen- 

 eral cytoplasmic reticulum. 



It has been assumed in the case of Ascaris that the cleavage 

 stages follow one another in such rapid succession " that the 

 character of the centrosphere has not time to change." Accord- 

 ing to Boveri's account of Ascaris, " Schon wahrend der Bildung 

 des Richtungskorpers finden wir das Archoplasma wenn auch 

 weniger verdichtet und nach aussen allmahlich sich verlierend 

 um das Spermatozoon angehauft ; noch friiher dagegen lasst 

 sich seine Existenz nicht nachweisen." 



In Limax, on the contrary, the peculiar type of centrosphere 

 that is characteristic of Ascaris is found in ova only during a 

 long period of quiescence, lasting from the time their devel- 

 opment in the ovary is completed until the formation of the 

 first polar globule. After that the centrosphere never again 

 acquires such a high degree of differentiation, although, as we 

 have seen, it still undergoes a series of changes that are repeated 

 during the maturation and fertilization stages of different ova 

 with the greatest precision. Kostanecki has attempted to 

 explain the different phases under which the " archoplasm " 

 of Physa appears as due to various changes that occur in the 

 structure of the cell in the course of development. These 

 changes consist in varying relations between the yolk, the 

 vacuoles, and the protoplasm, and they show that the formation 



