508 W. B. HARDY. 



nucleolus linked by scattered fibrils with irregular patches of 

 chromatin on their course to a deeply-staining envelope. 



The cell-substance of the columnar cells is granular and 

 turbidj the granulation mostly being fine. Picro-carmine or 

 hsematoxylin stains it only slightly. The ganglion-cells, on the 

 other hand, stain well with picro-carmine. 



The ectoderm of the proximal or gonophore-bear- 

 ing region is vastly different from that just described. In 

 the first place it is much thicker and more complex, being 

 composed of more varied elements. The ectoderm of the 

 distal region is about 30 to 35 fi thick, of the body 40 to 50 /x, 

 while that of the gonophore-bearing region varies from 50 fx 

 to 70 fx in thickness. The only other region in which the 

 ectoderm at all approaches it in thickness is in the foot. To 

 this fact we will return later. 



The second striking feature of the proximal ectoderm is that 

 its characters are not constant. It is most complex and 

 thickest in specimens killed in spring and early summer, while 

 in autumn it is not only much thinner (30 to 35 fx), but also 

 presents the appearance of being exhausted. A comparison 

 of fig. 2 with fig. 4 will render this abundantly evident. The 

 following description applies to specimens killed in March, 

 April, and May. 



Starting from the outside we have first a well-developed 

 cuticle, which overlies cells resembling the columnar cells 

 of the distal region, but, for the most part, shorter and 

 broader. They are composed of the same ill-staining granular 

 protoplasm, and the border between cell and cell is often so 

 indistinct that we might almost call this with Allmann a nucle- 

 ated protoplasmic layer. The proximal region is abundantly 

 armed with nematocysts, which, as was pointed out by Allmann, 

 are of two kinds. Here and there these may be seen wedged 

 between the columnar cells. The next following layer is a 

 fairly distinct one of large rounded cells engaged in the 

 manufacture of nematocysts. The protoplasm of these cells, 

 when stained with osmic acid, appears granular under 

 moderate magnification. With high powers (Zeiss ^th ob.) 



