REPOET OX THE HYDROIDA. 
XV 
one end to the summit of the capsule, and thence tapers away to a point where it is 
continued into the fine filament which is now seen to have uncoiled and extended itself, 
often to a great length, over the field of the microscope. 
F. E. Schulze 1 called attention to the occurrence of a fine process which in 
Syncoryne proceeds from the base of the cnidocyst towards the deeper parts of the 
ectoderm. Somewhat later 2 I described in Myriothela a remarkable modification of the 
thread-cell, which among other peculiarities is distinguished by the presence of a 
peduncle in the form of a long slender filament which is attached to the base of the 
cnidocyst, and thence extends among the cells of the ectoderm towards the deeper parts 
of this layer. These peduncles are manifestly of the same nature as those described by 
F. E. Schulze in Syncoryne. They may be designated by the name of cnidopods. 
Similar filaments have since been described by Grobben, 3 Ciamician, 4 and especially 
by Hamann, 5 who finds them in every Hydroid he has examined, and in all thread-cells, 
both large and small. He traces them through the thickness of the ectoderm as far as 
the mesosarc to which he believes them to be attached, and regards them as simply 
performing the part of mechanical supports of the thread-cells. He finds quite the same 
condition in the thread-cells of the tentacles of all craspedote Medusae, and in the 
Siphonophora ; also in Actinia, where these filaments had been already described by 0. 
and R. Hertwig. 6 
The cnidopods have also been described by Jickeli, 7 who has subjected them to a 
careful study in several Hydroids. He regards them as muscular, describes in them a 
tendency to fibrillisation, and believes that he has seen them in various states of 
extension and contraction. This view of the muscular nature of the cnidopods receives 
support from an observation by Claus, 8 who in a Medusa, Charybdcea marsupialis, describes 
thread-cells from which muscular fibrillse are sent off, and is further supported by an 
observation which we owe to Chun, 9 who has seen in the Siphonophora thread-cells which 
are clothed by a plexus of very fine muscular fibrillse which become united below into 
a stalk. Notwithstanding those facts, however, it does not seem that evidence has yet 
been adduced which would justify us in accepting as proved the muscular nature of 
the cnidopods. 
As already mentioned, Kleinenberg describes in Hydra, cells which lie superficially in 
the ectoderm, and send oft' from their deep surface tail-like prolongations which become 
1 F. E. Schulze, Ueber den Bau von Syncoryne Sarsii, 1873. 
2 On the Structure and Development of Myriothela, Phil. Trans., vol. clxv. 
3 C. Grobben, Tiber Podocoryne carnea, Sitzungsb. d. k. Akad. d. Wiss. Wien, 1875. 
4 J. Ciamician, fiber den feineren Bau und die Entwicklung von Tubularia, Zeitschr. f. wiss. Zool., Bd. xxxii. 
5 0. Hamann, loc. cit. 
6 0. und R. Hertwig, Die Actinien, 1879. 
7 Carl F. Jickeli, loc. cit. 
8 C. Claus, Untersuchungen iiber Charybdcea marsupialis, Arb. Zool. Inst. Wien, Bd. i. 
9 C. Chun, Die Natur und Wirkungsweise der Nesselzellen bei Ccelenteraten, Zool. Anzeiger, No. 99.* 
