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W. DE MORGAN AND THE LATE G. HAROLD DREW. 



varying size, often totally obscuring the nucleus, and the ectoderm cells 

 often partially or completely surrounded the tubules in the form of a 

 well-defined single cell layer. In some cases the cells of the tubules had 

 apparently undergone autolysis, and a space containing a little granular 

 cell debris was left surrounded by the ectodermal layer. 



Later the stages show little change or further degeneration. Sections 

 after 50 days show that a large proportion of the endodermal cells are 

 crowded with granules, and many of the tubules have disappeared ; on 

 the other hand, the ectoderm cells are quite undegenerated. At the 

 time of writing such restitution masses have been kept alive and in 

 apparent health for 60 days. 



endiub. 

 ect.- 



jrr. 





Fig. 9. >: 260. — Section through a small restitution mass 35 days old, showing the 

 formation of many granules in the endodcrm cells. Some of these cells are break- 

 ing down, so that the tubules are less distinct. The ectoderm cells remain healthy. 

 Ect., ectoderm cells ; end. tub., endoderm tubules ; gr., cytoplasmic granules. 



No signs of mitosis or any form of cell division was observed in any 

 stage. 



We would suggest that the changes that take place may be explained 

 as follows :— 



The endoderm cells are considerably more damaged in the process 

 of squeezing through the bolting silk than the smaller and tougher 

 ectoderm cells. They lose the majority of their cytoplasmic granules, 

 which are probably in the nature of a digestive ferment, and the nuclear 

 membrane is usually ruptured, causing certain changes in the nuclear 

 structure. As the cells begin to form aggregates the endoderm cells 

 become diffuse and join with each other by means of protoplasmic pro- 

 cesses to form a plasmodium, in the midst of which the comparatively 

 uninjured ectoderm cells are embedded. Certain ectoderm cells make 

 their way towards the periphery of the mass, or are left there by the 



