112 bulletin: museum of comparative zoology. 



we must at the same time admit a high degree of individuahty for the 

 autosomes. 



3. PJasmosovies and nucleoli. — One of the most puzzHng problems 

 that cytologists have to deal with is the behavior and function of the 

 so-called ' plasmosomes ' or 'nucleoli.' They apparently exhibit such 

 a variety of reactions to methods of technique, and exhibit such 

 varying relationships to other structures in the cell, that it is almost 

 hopeless even to attempt to classify them. That they play some 

 important role in the physiology of the cell, there is not the slightest 

 doubt, but what that role is, or what relation they bear to the question 

 of chromosome-individuality, are problems that are far from a solu- 

 tion at the present time. 



In my description of the tetrads A and B, I called attention to a 

 peculiar modification of one of the terminal granules of each. I 

 emphasized the fact that, in the case of tetrad A, this modified granule 

 furnished a means of identification for this element. Just what the 

 nature of this modification is, I cannot state definitely, but in the 

 pachytene stage it has the appearance of an expansion of a previously 

 condensed granule, and I have so treated it in my description. The 

 similar condition in B appears to arise in the same way, but in this 

 case there seems to be a more definite boundary to the modified gran- 

 ule, which thus resembles the plasmosomes, or "vesicles," described 

 by Carothers ('13). The expanded granule of A is usually not homo- 

 geneous, some areas within it appearing more dense than others. This 

 condition probably foreshadows that seen in the postspireme stages, 

 where it appears more like a collection of small granules, typically 

 tlu-ee in number. Miss Carothers described the 'vesicles' that she 

 found as being attached to spireme threads, and in some cases to 

 specific threads. Furthermore, she found that the occurrence of the 

 vesicles extended to several species, and, in some species, through 

 several generations of cells. I am indebted to Dr. McClung and to 

 Miss Carothers for the privilege of looking over some of the material 

 studied by the latter, as well as for the opportunity of studying slides 

 of other species ; I can confirm Miss Carothers's observations, and can 

 add that these so-called ' vesicles ' are present in nearly every species 

 of grasshopper that I have studied with this object in view. 



I believe that the modified granules in Phrynotettix can be homol- 

 ogised with the 'plasmosomes' of other species. I would especially 

 call attention to the fact that these structures are always attached to 

 chromosomes, and that, in Phrynotettix, at least, they always involve 

 a certain part of the chromosome to which they are attached. I 



