Cytological studies on the spinning glands of Platyphylax 

 designatus Walker (Phryganid). 



By 

 Will. S. Marshall and C. T. Vorhies. 



(Plate XX, XXI. 



The following work on the spinning- glands of the larva of Platy- 

 phylax designatus was undertaken with two quite different studies in 

 view; first, the anatomy of the glands and the shape and structure of 

 the peculiar nuclei they contain, and, second, an endeavor to ascertain 

 how the cells and their nuclei are affected by use. The cells in the 

 spinning glands of the Phryganeidae form, as in the Lepidoptera, an 

 exceedingly interesting subject for study; the ease with which the cells 

 and their peculiarly branching nuclei can be shown make them a desira- 

 ble object for cytological work. A review of the literature on the sub- 

 ject convinced us that a further study of these structures would be 

 profitable; a comparison of what we found in Platyphijlax with the 

 figures given by different observers of the nuclei from the same glands 

 in other insects, showed us that they were either in part diagrammatic 

 or differed in several respects from what we found in the Phryganid 

 we studied. Most ot the work already done has been upon the spinning 

 glands of the Lepidoptera; the similarity of the corresponding struc- 

 tures in the caddis-flies makes it seem probable that a careful inves- 

 tigation of the glands in this group of insects, which are here less 

 complex, will throw lighi: on those of the Lepidoptera. 



The second part of the Avork includes a minute study of the cell 

 and its nucleus from a normal gland (meaning by normal a gland 



