HISTOLOGY AND DEVELOPMENT OF MYRIOTHELA PHRYGIA. 533 



demands to regions quite remote. In other words, we must 

 suppose that the endoderm is not merely a collection of cells 

 each fighting for a share of the nutritive material to be 

 ultimately used by itself or by the ectoderm with which it 

 is anatomically in immediate relation, but rather that the 

 metabolic activities of the units of the endoderm throughout 

 its whole length are linked together into one consistent and 

 interdependent whole. 



What is the nature of that link, and how is the interchange 

 of material which it implies between widely separated regions 

 brought about ? That it is effected entirely by the laborious 

 passage of material from cell to cell throughout, perhaps, a 

 considerable length of the animal is, I think, an impossible 

 suggestion. Yet this process undoubtedly takes place to a 

 certain extent, and I think we may see in the palisade-cells 

 of the oral region, from the contents of whose enormous 

 vacuoles amorphous masses are precipitated by the action of 

 corrosive sublimate, a mechanism for facilitating such a process, 

 and whereby nutritive material may find its way even to the 

 lip, a region which during the early stages of the digestion of 

 prey of any considerable size must be more or less cut off 

 from the general somatic fluid. This same method of distri- 

 bution of nutritive material must also obtain between the 

 endoderm and the ectoderm, the interchange being facilitated 

 by the numerous pores which may be seen to penetrate the 

 supporting lamella when horizontal sections of that structure 

 are examined with the highest powers. But the stored nutri- 

 tive material of the foot can only be rendered available for the 

 body generally through the agency of the somatic fluid, and to 

 a certain extent histological facts support this conclusion. 



If we attempt to follow the further fate of the nutritive 

 spheres we find that two things may happen to them. They 

 may either undergo a gradual disintegration, their substance 

 becoming at the same time studded with pigment grains which, 

 after the nutritive sphere as such has ceased to exist, remain 

 as a little heap of dark granules, bound together by a scanty 

 amount of unstaining substance (fig. 25), while, as the dis- 



