27] LIFE HISTORY OF TREMATODES— FAUST 27 



where these special gland cells are not present, as in C. pellucida, the 

 parenchyma cells are more vesicular than where they are present. The writer 

 is in accord with Looss's view that there are no indifferent cells remaining 

 in the tail. Hence the tail, when separated from the body, can not meta- 

 morphose into a sporocyst or redia, as the older writers beheved (Pagenstecher, 

 1857:15). 



INTEGUMENT 



The covering of trematodes and cestodes has been the subject of con- 

 siderable controversy. Four main theories have been proposed. The Bloch- 

 mann theor}^ (1896) assumes that the cuticula of trematodes and cestodes is 

 a true morphological cuticula secreted by the hypodermis, as in other inver- 

 tebrates. A second theory, presented by Brandes (1892), postulates that 

 trematodes have no subcuticula in the true sense of the term, and what has 

 been considered as such is nothing more than the true parenchymatous con- 

 nective tissue. Nevertheless, the body covering is a true cuticula, secreted 

 by special glandular cells of epidermal origin just beneath the cuticula. The 

 presence of apparent nuclei in the cuticula has revived the old idea of Wagener 

 that the cuticula is a metamoiphosed epithelium. Goto has subscribed to 

 this theory in his study of ectoparasitic trematodes (1894:6-13), defining 

 three layers, an outer cuticula, a subcuticula, and a basement membrane. 

 This is also the interpretation Monticelli has put on the body investment of 

 Cotylogaster michaelis (1892:189), which he claims to possess an "ectoderma 

 sinciziale di aspetto cuticuloide. " More recently Gary (1909:646) has ad- 

 vocated this view. Pratt (1909:721) is inclined toward Leuckart's theory 

 that the cuticula is of parenchymatous origin, a derivative of the peripheral 

 portion of the parenchyma. 



The species of larval trematodes studied by the writer are uniform in 

 showing that the epidermal layer, developing into a syncytium in many cases, 

 is present in the early stages of the sporocyst, redia, and cercaria. In the 

 parthenitae, especially in the redia, this layer may persist until the germ 

 balls within are ripe and ready to escape. In the cercaria the epidermal 

 tissue is present in early life as a syncytial layer investing the larva. In the 

 mature cercaria it is sloughed off. The "cuticula," when present, arises 

 from below the epidermis. It is a discrete layer underneath the epidermis, 

 or it impregnates the epidermis from below. In the latter case the nuclei are 

 always superficial, usually rising above the surface as small tuberosities. 



In the monostome group, the redia possesses a syncytium of ectodermal 

 cells impregnated here and there with granules of a secretory nature. The 

 cercaria develops a well-defined epidermis which later (Fig. 37) becomes 

 syncytial and is sloughed off. Underneath this the "cuticula" is distinctly 

 cut off from the epidermis on the outside and from the mesodermal tissue 

 beneath. Among the latter are the special parenchyma cells with aciculate 

 pseudopodia, corresponding to Blochmann's " Epithelzellen " (1896:7). These 

 differentiated parenchyma cells have no connection with the "cuticula" in 



