The Behaviour of the Nucleolus during Oogenesis. 131 



corrosive acetic or Bouin (with acetic), and stained with Mann's 

 methyl blue eosin, I find that the chromosomes of the spermatocyte 

 during reduction division appear amphophile with distinct basophil 

 preponderance, and later the same chromatinic substance forming 

 the head of the spermatozoon appears brilliantly red. Gatenby 

 finds a similar thing in Saccocirrus (6'), after fixation in Petrunke- 

 witsch and staining in Ehrlich's or Delafield's heematoxylin and 

 eosin or Biebrich scarlet. It is therefore absolutely unjustifiable 

 on staining tests alone to call a basophil staining nucleolus a 

 chromatin body, or to deny that an oxyphil nucleolus may contain 

 chromatin. 



It is also known that the fixative used mav determine to a 

 great extent the nature of the suljsequent staining. Jorgensen, in 

 his work on Patella, found the nucleolus ampliophile with basophil 

 preponderance in the youngest oocytes, while in the species of 

 Patella described in this paper the nucleolus was in most cases 

 distinctly oxyphil, although there were exceptions where it could 

 be described as amphophile with distinct oxyphil preponderance. 



I attribute this difference in a large degree to the fixative used, 

 for in making preparations with Limnsea material, I find that 

 after fixation with Bouin's fixative the nucleolus stains oxyphil, 

 while with prolonged fixation in corrosive acetic it stains basophil. 



Observations such as these detract from the value of much 

 work on nucleoli and chromatin based upon staining reactions 

 alone. Also we know that differences in staining may be the 

 result of differences in the surface membrane of the objects stained. 

 In the case of Patella however, where there is a functional 

 differentiation of the nucleolus into two parts, I consider it is 

 justifiable to assume that the difference in staining reactions of 

 oxyphil and basophil nucleoli corresponds to a difference in 

 chemical constitution. That there is a difference in the chemical 

 composition of the nucleoli of different animals has been shown 

 by Jorgensen {9), who, as the result of digestion experiments with 

 pepsin, divides nucleoli into three classes — namely, those inmiedi- 

 ately digested, those digestible after prolonged exposure to the 

 ferment, and those indigestible to begin with, but soluble later. 



Jorgensen concluded " that we can only say with certainty that 

 the nucleolar substance is a functional organ during egg growth, 

 and is no worthless metabolic product " ; and all that we are justified 

 in adding at present is that it is in several species related to the 

 formation of yolk, while in others it gives rise to " secondary 

 nucleoli," and that it may stand in some functional relationship 

 to the formation of the small condensed chromosomes from the 

 much spread out structural forms the latter assume during the 

 various formative processes in the o5cyte, but such a hypothesis 

 does not imply any interference with the integral continuity of the 

 chromosomes throughout the germ cell cycle. 



