.322 



THE INHABITANTS -OF THE SEA. 



the antechamber of the alimentary canal, which is barely 

 distinguishable into gullet, stomach, and intestine, and always 

 convoluted or folded once on itself. The Tunicata are ex- 

 clusively marine, and widely spread from the arctic to the 

 tropical seas. All of them are free during the earlier parts of 

 their existence ; some remain permanently so (Pyrosomidae, 



^^r 



Clavellina producta. Group of two adult 

 and several young individuals, mag- 

 nified about five times. 



c Branchial orifice. <r. Branchiae i. Anal orifice. 



i. Stomach, o. Heart, v, u' f u". Reproductive 

 buds, springing from the abdomen of the adults. 



Aacidia m&mmillata. 



a. Branchial orifice, open. 



b. Anal orifice, closed. 



Salpae), but the generality (Ascidise, Botrylli) become fixed to 

 shells and other marine bodies ; some exist as distinct individuals 

 (Ascidise, Cynthia), whilst various degrees of combination are 

 effected by others (Botryllus, Clavellina, Pyrosoma), and some 

 are simple in one generation and combined in the next (Salpae). 



