Martin, A Note on the Occurrence of Neniatocysts and Similar Structures etc. 259 



II. (3) TnrbeltfU'ia. 



The references to the early literature on the occurrence of 

 Neniatocysts in the Turbellaria can be found in my paper "On the 

 Neniatocysts of Turbellaria", Q. J. M. S., Vol. 52, 1908. 



In dealing with the group Rhabdocoelida in which the nomen- 

 clature appears to change in a somewhat kaleidiscopic fashion, I 

 have decided in this paper to use the names given in von Graff's 

 volume on the Turbellaria in Bronn's Tierreich. In some cases 

 therefore the names in this list do not agree with the names given 

 in my previous paper which were taken from von Graffs Mono- 

 graph on the Turbellaria. 



It appears to me that the Neniatocysts described in the Rhab- 

 docoelida can be treated in two categories, (a) Pseudocnidae, 

 (b) Cleptocnidae. 



(a) Pseudocnidae. 



Under this category I am inclined to place the cases described 

 for the occurrence of Neniatocysts in Alaurina viridirostrum, Poly- 

 cystis Nayelii, Polycystis niamertina, Triyonostomum armatum, and 

 Otoplana setosa. 



I have given the evidence on which I am inclined to regard 

 the so-called Nematocysts of Polycystis Nagelii and P. mamertina 

 as rhabdites possibly specialized for prehensile purposes in my 

 former paper. The Nematocysts described by Jensen in Triyono- 

 stomum armatum have already been placed by von Graff in the 

 category Sagittocysts, though it is evident that he does so with 

 some feeling of reserve (see p. 2040). 



,,0b diese, bei den Acocla (S. 1916) in so charakteristischer 

 Auspragung vorhandenen, spindelformigen Korper mit einer in 

 Fliissigkeit suspendierten Zentralnadel bei den RJtabdocoelida in der- 

 selben Weise ausgebildet sind, ist einstweilen noch fraglich. In- 

 dessen gehoren wahrscheinlich hierher die langen, hohlen, stab- 

 formigen Korper von Trigonosfomum armatus (Jens.), welche nach 

 Jensen (335, p. 10; III, 15 a, u. a., 19) in zwei, im Beginne der 

 zweiten Korperhalfte anfangenden, die Mitte der Bauchflache ein- 

 nehmenden Strafien nach hinten ziehen, urn nahe dem Hinterende 

 nach aufien abzubiegen und an die Hautoberflache zu treten. Sie 

 haben eine Lange von 34, sind langgestreckt, in ganzer Lange gleich 

 breit und an den Enden abgestumpft und jedes dieser Stabchen 

 soil einen feinen Zentralfaden besitzen, den jedoch Jensen niemals 

 ausgestofien sah." 



In this category of Pseudocnidae I am inclined to place the 

 oval bodies described by Meres chk o wsky as Nematocysts in 

 Alaurina rindirostnnn. In none of these cases has the expulsion 

 of the thread been described, but the state of affairs is very different 



