1869.] and Membranipora Bengalensis. 35 



of concentric fibres, - the transverse plication becomes somewhat more 

 distinct than it was before, and the immediate neighbourhood of the 

 suckers slightly rises to short, transverse prominences. The greater con- 

 traction of the pigment layer also makes the greenish bands of the septa 

 more distinct, though the entire body possesses a slight tinge of the 

 same colour. The cinclides, especially those placed near or on the collar, 

 become rather widely open, and others are distinctly traceable ; the 

 acontia are numerously ejected on different places of the body, and the 

 general transparency has again diminished as compared with the former 

 position. 



Besides these three, so called normal, positions* of a Sagartia, there 

 are others which the animal assumes under certain abnormal conditions, 

 generally resulting from ill health, and being produced, either by 

 excessive heat or light, or by a change in the saline constituents of the 

 water, &c. Some of the principal forms, as observed on one and the 

 same specimen, are represented in figures 6 to 9, on plate X ; but I will 

 defer the remarks upon these, until I come to speak of the physiology 

 and the habits of the animal. 



b. Anatomical Structure. 



In order more easily to understand the general anatomical structure 

 of the animal, I must direct the reader to the vertical section, as re- 

 presented in figure 3 on plate XI. This section is taken only in half 

 of the diametral length, being sufficient for our purposes, and the dif- 

 ferent letters, noted in this figure, have the following significations : — 

 a, base ; b, column ; c, collar ; d, disc ; e, tentacles ; g, throat ; 

 h, larynx ; i, stomach, or internal cavity ; k, craspeda ; 1, acontia ; 

 m, ovaria, or the reproductive organs ; n, cinclides, or pores in the 

 integument for the purpose of emitting the acontia. I shall now 

 briefly describe these parts as much as possible in the same order, in 

 which I have just mentioned them. 



The entire body of the Sagartia is surrounded by an external, 

 mucous layer, which chiefly consists of numerous, oval cnidoe, and 

 sparingly dispersed green pigment cells. 



a. The base is, as already stated, a more or less round disk ; on 

 Avhich the septa are distinctly traceable (pi. X. fig. 5), being of con- 

 * Being observable in most other Halihhoda. 



