44 THALASSICOLLID.E. 



CHAPTER V. 



THALASSICOLLID^. 

 I. External characters. — 2. Organisation. — 3. Acanthometrse. 



1. External characters. — The group of 

 TJialassicollidce includes certain gelatinous marine 

 animals which, though abundant in most seas, 

 would appear to have remained altogether unno- 

 ticed until the year 1851 when Mr. Huxley first 

 directed the attention of naturalists to the pecu- 

 liarities of structure which they present. They 

 can scarcely be said to possess any determinate 

 form, and seem to be destitute of the power of vo- 

 luntary motion, being usually found floating near 

 the surface of the water. In size they vary from 

 an inch downwards. 



2. Orgasaisatioii. — Sphoirozoum 'punctatum^ 

 one of the most abundant of these animals, 

 presents in many cases a somewhat ovate body 

 constricted in the centre {fig. 9, ci), and is found 

 to consist of a transparent, colourless, gelatinous 

 substance, destitute of structure, surrounding a 

 large internal cavity. Enclosed in the gelatinous 

 mass are a number of isolated, minute, "cellae- 

 form bodies " (e), each of which consists of an 

 external membrane filled with granular contents, 

 mthin which a " clear fatty-looking " nucleus may 

 be observed. 



The gelatinous mass frequently contains mi- 

 nute, yellow, spherical cells, these being either 

 irregularly diffused through its substance or 

 gi'ouped around each of the cellseform bodies. 



