of a millirnetei* outward from the ocellus. In this area of 

 degeneration the entoderm cells are broken down, the support- 

 ing membrane has disappeared, and the inner boundary of the ec- 

 toderm is indistinct. The axial m.ass of this part of the ten- 

 tacle is made up cf loose particles of a finely granular sub- 

 stance in which, in Fig. 42, we see many small and deeply stain-r 

 ed nuclei. In Fig. 41 these nuclei are not so prominent and 

 there are numbers of green cells that apparently escaped into 

 the central mass when the supporting membrane broke down. There 

 is evidently a free communication between this mass of disinte- 

 grating material and the digestive cavity thro-agh the rhopalial 

 canal . ' 



I The method by which the shortening of the tentacles is 

 brought about would seem to be as follows : The axial cells 

 adjoining the cells that bear the concretion (Fig. 40) first 

 break down. Why they should do so, and at this particular 

 time, I cannot say. This disintegration proceeds centrifugal- 

 ly and it is accompanied by a dissolution of the supporting 

 membrane. The ectodermal cells then either begin here and 

 there to break down while still in place and the resulting de- 

 bris is squeezed into the central cavity ; or else, the cells 

 migrate, or are squeezed inward and then disintegrate. 

 The continuity of the remaining ectoderm is maintained, how- 



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