Cotylogastor occideutaliis ii. sp. 609 



any distiiict Separation between the cilia bearing cells and the thinner 

 portion of the integument covering the rest of the body have con- 

 vinced mc that the outer layer of the erabryo is a modified epitheliuni 

 as Braun, Monticelli and others have claimed to be the case in 

 treniatodes generally. In the adult no trace of nuclei is perceptible 

 tho' we must consider it probable in vievv of Voeltzkow's observations 

 on Aspidogaster that the embryo develops directly into the adult. If 

 this be true the integuQient of the adult must be regarded as fun- 

 damentally a modified epithelium lacking all traces of nuclei and cell 

 outlines. Whether other processes have subsequently occurred to 

 modify this primitive or embryonic condition must remain an open 

 question. The evidence from various sources seems to agree in show- 

 ing that the integument of trematode embryos is a modified epithelium. 

 I am not convinced however that it is safe to assume as some have 

 done that no additional or supplemental process has operated to pro- 

 duce the often very greatly increased bulk of material in the covering 

 of the adult animal. A reexamination of my sections of larval stages 

 of Sticliocotyle (Nickerson '95) falls to show any trace of nuclei in 

 the integument. In view of the Statement of Odhner ('98) that the 

 adult attains a length of 105 mm, more than 15 times the length of 

 the largest described embryo, it is difficult to understand how such 

 increase of the integument as this necessitates can occur without therc 

 being a growing zone somewhere present and I am not acquainted 

 with any biological conception of growth which does not involve the 

 presence and participation of nuclei. The observations of Pratt ('98) 

 upon Apoblema (= Hemiurus Rud.) seem also to show that another 

 process than obliteration of nuclei and cell boundaries of an epithelium 

 must be taken into account in explaining the conditions in the in- 

 tegument of that form. It seems clear from such cases that there 

 must be a secondary or supplemental process coucerned in the for- 

 mation of the integument of the adult but questions concerning the 

 uature of this process can be answered at present only by hypotheses. 

 A Cluster of large elongated cells represented in Figs. 17, 19 and 

 21 is present in the anterior end of the embryo. The bodies of the 

 cells lie above the pharynx and send slender processes forward which 

 reach to the surface at the extreme tip of the body (Fig. 21). The 

 number of these cells is small, probably not above four. The cyto- 

 plasm is filled with granules which stain with acid dyes (Tropaeolin). 

 The form and relations of these cells together with the condition of 

 the cytoplasm indicate a secretory function. Their number, form and 



40* 



