420 Univt rsity of California Publications in Zoology. ["Vol. 6 



situated over the enlarged hypodermal cell which produces it. 

 Nothing of the sort exists in trematodes and cestodes. The sub- 

 cuticular cells beneath the hooks and spines do not differ in size, 

 number or arrangement, from the adjacent cells and in the 

 monogenetie trematodes, which are often provided with gigantic 

 hooks, no subcuticular cells at all are present." 



In Gyrocotyle the subcuticular layer of cells is much increased 

 in thickness in tin neighborhood of a spine and is closely related 

 to it. 



A question of far greater difficulty is that of the function of 

 the subcuticular cells. If not related to the formation of the 

 cuticula, what is their function? Pratt makes two suggestions; 

 first that they are secretory in function, forming an antibody 

 for the protection of the worm from the chemical action of the 

 medium in which it lives. This is supported by the fact that 

 these cells are altogether lacking in monogenetie trematodes. A 

 second suggestion (see Looss, 1894). is that these cells constitute 

 an undifferentiated embryonic layer, from which new cells of 

 various tissues are formed during the lifetime of the animal. 

 The only evidence in support of this theory is the statement that 

 in certain individuals known to be of advanced age, the sub- 

 cuticular laj'er was greatly reduced. 



The glandular theory finds uo definite support in the con- 

 ditions in Gyrocotyle. The unmistakable gland cells here present 

 are found as above noted in the central core of the body, not 

 in relation to the peripheral layer. The statement made by 

 previous investigators that the subcuticular layer gives rise on 

 the inner surface of the rosette folds to gland cells has not been 

 verified in the writer's preparations. However, this does not 

 militate against the possible glandular nature of these cells. The 

 intense staining reaction of the cytoplasm of at least some of 

 these cells recalls the appearance presented elsewhere by un- 

 mistakable gland cells. 



Looss 's suggestion seems hardly susceptible of proof or dis- 

 proof. It is difficult to believe that the layer of cells so closely 

 related in position to the cuticula, varying in thickness with its 

 thickness and increasing in the region of special cuticular struc- 

 tures such as spines, should be totally unrelated to the body- 



