174 



BIOLOGICAL LECTURES. 



In this interesting series of changes we observe a granule 

 which appears to be a derivative of the chromatin reticulum, 

 applying itself to a true nucleolus, and by gradually absorbing 

 the substance of the latter, becoming a large chromatin nucle- 

 olus. Is it a specially modified portion of the chromatin retic- 

 ulum which is predestined to undergo this change? It would 

 seem more probable that that portion of the chromatin reticu- 

 lum lying closest to the true nucleolus would be the portion 

 selected to grow. 



The cells of the extremities are the producers of the cutic- 

 ular structures of the latter, and their large size, amoeboid 

 nuclei, and chromatin nucleoli are all evidently occasioned in 

 the course of this production ; and beneath each of the cuticu- 

 lar spines, which occur elsewhere on the body surface, lies a 

 mass of cells much larger than those of the surrounding hypo- 

 dermis, the relatively enormous amoeboid nuclei of which con- 

 tain each a chromatin nucleolus. There can be no doubt that 

 these chromatin nucleoli have been formed in the same manner 

 as those in the cells of the extremities, though I have not seen 

 the various stages of their formation. And in the body cavity 

 are enormous cells, each with an amoeboid nucleus and a chro- 

 matin nucleolus, which are, undoubtedly, cells which at one 

 time were situated within the hypodermis and functionated as 

 spine producers, and later lost this connection, falling into the 

 body cavity, where they increase greatly in size and probably 

 fulfil some new function. 



In cells of other tissues of the Carpocapsa larva chromatin nu- 

 cleoli are also to be found, as in the intestine and salivary gland 

 cells ; but their genesis could not be traced by me, as it was 

 for the hypodermal cells of the extremities and of the stomo- 

 daeum and proctodaeum ; earlier ontogenetic stages might give 

 the solution of the question. 



What is the meaning of the evolution of such chromatin 

 nucleoli — structures which have not frequently been observed 

 in cells, and the genesis of which has not heretofore been 

 followed.? The chromatin is a living, and, from the morpho- 

 logical standpoint, most important substance. So that, if my 

 observations prove the chromatin origin of the chromatin nu- 



