The Histogenesis of Cysticercus pisiformis. 229 



origin and hence must be so in Cestodes, has no more weight than 

 the argument that all other invertebrates have an epithelium and 

 hence the Cestodes must likewise possess one; or than that of 

 Blochmaxn (1896, p. 3), that ''Cestoden und Trematoden müssen ein 

 Epithel haben. Sie haben es auch". 



The fourth argument for this theory likewise falls somewhat 

 outside the scope of this paper, since gland cells except flame cells 

 are wanting in Cj'sticercus pisiformis. It may be remarked 

 in passing, however, that there has been no evidence presented to 

 show an epithelial origin for these cells, at least in the Cestodes. 

 A gland cell figured by Pintner (1903, fig. 29) shows very clearly 

 an intimate union of this cell with the adjacent parenchyma. This 

 is at least suggestive of a possible parenchymatous origin for these 

 cells, in spite of the statement of Blochmann (1896, p. 3) that 

 •'Diejenigen, welche unsere Thiere nur aus Parenchym bestehen lassen, 

 müssen also die weitere unwahrscheinliche Annahme machen, dass 

 einzellige Drüsen bei ihnen aus dem Parenchym (Bindegewebe) her- 

 vorgehen, was sonst nirgend im Thierreich festgestellt ist". And the 

 mere fact that in other animals glandular elements are epithelial in 

 origin, is, as I have endeavored to show in my criticism of argument 

 3, not conclusive proof that they are so in the Cestodes. 



The claim that the sub-cuticula performs the function of ab- 

 sorption in Cestodes is probably correct. There is, however, no 

 evidence to show that this function may not be partly performed 

 also hj parencln-ma fibres which enter the cuticula. 



In the discussion of Bügge's work the reasons for rejecting the 

 theory of an epithelial origin for the flame cells have already been 

 stated and need not be repeated at this point. 



Considering now the arguments which have been advanced 

 against the epithelium theory: The fact that the sub-cuticular cells 

 are in union with the underlying parenchyma does not in itself 

 alone constitute a valid objection to this theory, nor does the fact 

 that they may assume a stellate form and be widely separated from 

 one another by intercellular bridges, thereby strictly simulating the 

 appearance of a parenchyma tissue. For, as has been pointed out 

 by Blochmann (1896, 1897), Hein (1904) and others, there are 

 occasional instances in which a true epithelium maj^ lose its epithelial 

 character to assume the character of parenchyma. 



The most recent opponent of the epithelium theorj^, Bott (1896, 



