398 R. VON LENDENFELD. 



control over these movements by means of the subepithelial 

 nervous layer situated below the cnidoblasts. 



2. The granular peduncle is a nerve-fibre connecting the 

 protoplasmatic mantle of the Nettlecell with the nervous system 

 of the animal. 



3. By means of this the movements of the protoplasmatic 

 mantle can be controlled. 



4. The explosion of the cnidoblast is caused by the contraction 

 of the plasmatic coat which surrounds the capsule, and which 

 in Physalia (Chun, 1. c.) has partly been converted into a 

 network of muscular fibres. 



5. The plasmatic contractile coat of tbe cnidoblast is incited 

 to action by the cnidocil. If anything touches the cnidocil then 

 the plasma mantle contracts and the tube is shot forth. 



6. The animal can, however, by its volition prevent this 

 reflex action by means of the nerve-fibre connecting the cnido- 

 blast with the ganglia cells below. In this way the explosion 

 may be prevented even if the cnidocil be touched, if this be the 

 wish of the animal. 



We find, accordingly, that the complicated machinery of 

 nerve-centres controlling reflex actions of a low order in man 

 and the higher animals is found also in tljese low forms of 

 animal life, the Coelentera. 



The Ctenophora, which are destitute of cnidoblasts, possess 

 in their stead certain structures, the "Klebezellen^^ of Chun and 

 the " Stiftzellen "^ of Hertwig, which appear homologous with 

 these Nettlecells in the Ctenophora. Their action is very different 

 and they do not explode like the cnidoblasts of Polypomedusse. 



It seems, however, probable that they are in a similar way 

 subject to the control of the animal, as is the cnidoblast. 



' These are, according to my investigations of the histology of Nais cor- 

 digera, Les., (7), not a sensitive apparatus, as the brothers Hertwig had 

 assumed, but stinging hairs. 



