74 



Mr. L. Hog Den. 



Agar points out, in so many cases where earlier accounts (many Orthoptera, 

 Platyhelminthes and Amphibia) appeared to support the telosynaptic 

 interpretation, later examination of the very same animals provided evidence 

 of parasynapsis. 



Even accepting provisionally the possibility of pairing of both types in 

 reduction among different animals, a difficulty emerges from the study of 

 the premeiotic prophase and telophase, which to the author's knowledge 

 no animal cytologist, who has of recent years advocated telosynapsis, has 

 attempted to dispel. That many plant cytologists have succeeded in doing 

 so is well known ; and it has already been insisted in a previous paper that 

 the similarities of the meiotic phase in animals and plants may have been 

 grossly exaggerated. The possibility of relating the leptotene stage to the 

 previous telophase in animals emphasises the dissimilarity further : that is, 

 if actual synapsis in plants accompanies second contraction. Since modern 

 research has failed to find any confirmation for Flemming's conthiiiotis spireme, 

 the task devolves on those luho adhere to terminal as opposed to lateral conju- 

 gation in animals to state {in terms consonant with the known hehaviour of the 

 chromosomes in the meiotic and prertieiotic nucleus) at what precise point tliis 

 process is supposed to take place. 



The So-called Double Nucleolus. 



Though the belief in the individuality of the chromosomes as persistent 

 units of cell structure increasingly finds favour among those who study the 

 problems of the cell, it is idle to overlook the fact that many current 

 observations are clearly antagonistic to it. One such has been dealt with in 

 the previous paragraph ; a second, the question of the " chromidia " and so- 

 called secondary nuclei has been touched upon in previous studies (6). On 

 this point the behaviour of the plasmosome in the oogenesis of Libellula 

 (figs. 36-39) is specially instructive; and a brief consideration of it will 

 make clear how McGill was misled in describing the origin of the double 

 nucleolus of Anax. 



A reference to Jorgensen's work (14) will amply illustrate the capricious 

 changes in staining capacity of the plasmosome accompanying the growth of 

 the oocyte. Most commonly the nucleus of growing oocytes in preparations 

 of Libellula fixed with Flemming's reagent and stained with Auerbach's 

 method, exhibit a nucleolus consisting of a large medullary portion which is 

 fuchsinophil and a surrounding cortex stained with methyl green. Precisely 

 the same type of nucleolus is described by McGill, who faihng to find typical 

 stages succeeding contraction and led astray by the belief that fuchsin and 

 methyl green are an infallible means of differentiating chromatin from other 



