382 



—--'■)h. 



1/ 



\ 



larger and less regular than iu the earlier stages and in most cases 

 there is a considerable enlargement of the linin threads. 



The plasmosomes have never been observed at this time and in 

 this respect the nuclei are entirely different from both the earlier and 

 later stages. 



The karyosomes in these nuclei are arranged in a fairly definite 

 manner, being generally so grouped that they form a wide peripheral 

 layer. In addition to this peripheral layer there are usually a num- 

 ber of karyosomes lying 

 in or near the axis of 

 the nucleus, as observed 

 by Rabl in Pristiurus. 

 The karyosomes of the 

 peripheral layer vary 

 widely in form and size, 

 often they are greatly 

 elongated in the trans- 

 verse planes of the nu- 

 cleus. The axial karyo- 

 somes on the other 

 hand are most fre- 

 quently elongated in a 

 direction corresponding 

 to the long axis of the 

 nucleus. It is of im- 

 portance to here note 

 that this type of nu- 

 cleus is found, in the 

 26 mm larva, most fre- 

 quently in the new 

 muscle cells lying at 

 ^^^vl^' the upper, lower, and 



Fig. 3. outer margins of the 



myotome. 

 In the adult muscle cell we find the nuclei are no longer confined 

 to the periphery but are scattered throughout the sarcoplasm and among 

 the fibrillae. One of the most striking differences observed when the 

 nuclei of the adult are compared with those of the 26 mm stage is 

 the faint staining capacity of the former as indicated in the figures. 

 The nuclear membrane likewise takes the various basic stains less 

 readily. The linin network can be made out only with difficulty in 



^ 



1. 



- p. 



1 



Fig. 



