Japanese Tricladida Maricola. n 



"in Ect. Umnll. In the species examined there uocurs no indica- 

 tion of the cuticular wall observed in several forms l)y Wilhelmi 

 (71) and others. 



ïnrning attention to the variations, pointing out the resem- 

 blance between the insunken epidermis of the Turbellaria and 

 the ' epidermis ' of the Trematodes and Cestodes, the probable 

 ■descendants of the former group, von Graff (24) has stated as 

 follows: — "Berücksichtigt man, dass in der ursprünglichsten 



Familie (Geoplanidae) ein normales Epithel angetroffen 



wird, so kann man in den eingesenkten Epithehen überhaupt 

 und speciell in dem der Kriechleiste nur einen secundären Charak- 

 ter erkennen — einen Charakter, der erst in den beiden am weitesten 

 differenzirten Familien der Rhyncodemidae und l)ipaliidae auftritt 

 und bei letzterer seinen liöchsten Ausbildungsgi-ad erreicht hat. 

 Hier ergreift der Process der Einsenkung bei manchen Formen, wie 

 Plac. keiüe7isis, das gesammte Körperepithel und man könnte sagen, 

 dass diese Species und die ihr im Bau des Epithels zunächst- 

 stehenden Bipaliiden im Begriffe sind, die Epithelform der Trema- 

 toden und Cestoden zu acquiriren." In the endoparasitic Trema- 

 todes and Cestodes the body is generally invested by a cuticular 

 wall, while in the ectoparasitic Trematodes regarding as the 

 probable intermediate group of the former groups and Turbellaria 

 there appear to be found some epidermal variations. The epider- 

 mis retains in some cases either the cellular or the cuticular 

 feature over the whole surface of the body. Frequently there 

 occur some species, in which the cuticular wall partly consists of 

 the cells, or contain a number of nuclei at ii-regular intervals, as 

 for example in the primitive cestode Amph'dlna — Salensky (52) as 

 well as in several Trematodes {Bucephahn^ — Zteglfr (76); Ccr- 

 carla — Schwarze (54), PIeckert, 1SS9 ; ß^oiioslomam muta/nle, 'Brm'm 

 (8); Nemat/iobothriu7n molae SLYid Distomum — Macxaren (42) ; Coti/- 

 logaster — Ni(;kerson (46), etc.) In some specimens it is found that 

 the cuticular wall, in its earliest stage, is composed of the cells 

 which in later stages become the cuticula, the cytoplasma chang- 

 ing its character and the nuclei being obliterated gradually. To 

 judge from the epidermal variations just mentioned, it seems that 



