Miscellaneous. 243 



proper nomenclature of the sides and ends of these animals, a sub- 

 ject on which much confusion has prevailed. Particular attention 

 is called to the existence of an organ hitherto undescribed — a cylin- 

 drical, elongated body, like an internal shell, — here termed the " en- 

 dostyle," which lies in the dorsal sinus, and has hitherto been con- 

 founded with the "dorsal folds" of Savigny. A peculiar system of 

 delicate transparent vessels, taking its origin in the stomach and 

 ramified over the intestine, is described and its nature inquired into. 

 The organs of reproduction are next inquired into. The young 

 in the Salpa democratica constitute a " Salpa-chain," and are shown 

 to arise by gemmation from a tubular diverticulum of the vascular 

 system of the parent. In the course of their development they take 

 the form of the S. mucronata. 



The young in the Salpa mucronata again is shown to be solitary, 

 and attached to one point of the respiratory chamber of the parent 

 by an organ which exactly represents in its structure a rudimentary 

 mammiferous placenta, except that in the Salpce the " villus" is 

 formed by the maternal system, the " placental cell" by the fcetal 

 system. But the foetus here is not produced by gemmation, as in 

 the preceding case, but by a true process of sexual generation. 



Every Salpa mucronata contains at one period of its existence a 

 solitary ovum, and a testis, which is a ramified gland surrounding 

 the intestine, and hitherto confounded with the liver. The solitary 

 ovum becomes fertilized, pushed out into the respiratory cavity of the 

 parent, and remains connected with the latter until it has assumed 

 the form of the Salpa democratica, v hen it becomes detached. 



Chamisso's formula therefore, " that the parent Salpa produces 

 an offspring different from itself, which again produces an offspring 

 different from itself, but similar to its parent," is perfectly correct, 

 only the word " produce" has two meanings — in the one case signi- 

 fying a process of gemmation, in the other of true sexual generation. 

 The author next proceeds to describe the anatomy of Pyrosoma, 

 and to point out its general harmony with that of Salpa. He shows 

 the existence of an endostyle — a system of ramified intestinal tu- 

 bules — and of other organs precisely resembling those described in 

 the latter genus. The " hepatic organ" of Savigny is the testis, 

 while the female generative organ consists of solitary pedicillate 

 ova. The arrangement of their parts is essentially the same as in 

 Salpa, only that the foetus does not appear to be developed in pla- 

 cental connexion with the parent. 



The Pyrosomata increase by gemmation also, but the gemmae are 

 solitary and do not form chains, becoming developed like those of 

 the ordinary compound Ascidians between the pre-existing forms. 



In the next section, the zoological relations of the Salpa? and 

 Pyrosomata, with the other Ascidians, are inquired into. The au- 

 thor endeavours to show that there is no essential difference of or- 

 ganization between the ordinary Ascidians and the Salpa;; that the 

 two forms grade insensibly one into the other ; and that there is, 

 therefore, no ground for breaking up the great ascidian family into 

 the two subdivisions of Monochitonida and Dichitonida. 



With regard to the theory of the " alternation of generations/' 



.16* 



