252 Martin, A Note on the Occurrence of Neraatocysts and Similar Structures etc. 



(5) Spirocysts. 



These structures, as far as I am aware, are confined to one 

 group of the Coelenterates the Anthotoa. They are hollow capsules 

 containing a solid spiral thread, in which the thread is discharged 

 as a whole and is of course not everted. In the following table 

 an attempt has been made to distribute the various structures which 

 have been described as Nematocyts in the various animals into 

 these five categories. The evidence on which this distribution is 

 based will be found in a later part of this paper. 



Part II. Xematocysts and Similar Structures in (1) The Protozoa. 



In this part of my paper I do not propose giving any detailed 

 account of the polar capsules of the Cnidosporidea, or the Tricho- 

 cysts of Ciliates. On the other hand, I propose to discuss in some 

 detail, 



(1) The Cleptocnidae found in certain Ciliates and Acinetaria. 



(2) The Cleptocnidae of the Dinoflagellate Polykrikos. 



(3) The Pseudocnidae of Epistylis Umbellaria. 



The polar capsules of the spores of the Cnidosporidea are small 

 chitinous (?) pear shaped capsules containing a spirally coiled thread 

 and developed singly in special cells, the Capsulogenous cells. The 

 thread can under suitable conditions be everted in a manner ab- 

 solutely analogous to that in the exploding Nematocyst of a 

 Coelenterate, and probably serves for the attachment of the spore 

 to the gut wall of the host, cf. Doflein, p. 861. As regards the 

 development of these structures Awerinzew states on page 101 

 of his ,,Studien iiber parasitische Protozoen", 1909. 



,,0bgleich es mir, infolge der unbedeutenden Grofie des Ob- 

 jektes, nicht gelungen ist, die Bildung der Polkapseln in den Sporen 

 von Ceratomyxa drepanopsettae in erschopfender Vollstandigkeit zu 

 verfolgen, so erweist sich doch die Entwickelung dieser Kapseln 

 nicht allein in ihren allgemeinen Zfigen, sondern auch in alien 

 Einzelheiten, als durchaus ubereinstimmend mit der Entwickelung 

 der Nesselorgane bei den Coelenterata (vgl. Iwanzoff, 1897)." 



The Trichocysts of Infusoria have been defined by Doflein 

 in the following passage, p. 285 of his ,,Lehrbuch der Protozoen- 

 kunde" 



,,Trichocysten sind im Kortikalplasma liegende, besonders 

 bei holotrichen Infusorien weitverbreitete stabchen- und spindel- 

 formige Gebilde, welche durch ihre starke Lichtbrechung auffallen. 

 Sie sind vielfach in kleinen Gruppen an verschiedenen Stellen im 

 Korper angehauft oder ziemlich gleichmiiSig iiber dessen Oberflache 

 verteilt, zu welcher sie senkrecht stehen. Bei Einwirkung von che- 

 mischen Reizen oder von Druck werden sie ausgeschnellt, wobei 

 sie zu langen Faden werden, deren Enden bei manchen Infusorien 



