492 Miscellaneous. 



ornament quite so well as might be desired, the agreement in this 

 character between my specimen and the original figures and descrip- 

 tion is such as to make the specific determination also a matter of 

 certainty. 



On the Anatomy of Pyrosoma. By M. L. Joliet. 



Growth of the Cohny. — All the observers who have paid attention 

 to Pyrosoma have remarked that the closed extremity of the colony 

 is occupied by four ascidiozoids. According to Savigny and Le- 

 sueur these are the four primitive individuals developed in the egg 

 itself. As regards Pyrosoma elegans, in which, as stated by Kefer- 

 stein and Ehlers, the endostyle is on the side of the common orifice, 

 I cannot say how this may be ; but in Pyrosoma gvjanteinn things 

 are diff'erent. Panccri has already remarked that the terminal 

 ascidiocoids are destitute of those muscular cords which terminate 

 at the periphery of the common cloacal aperture, and which are 

 possessed by the primitive ascidiozoids. Moreover, in P. giganteum, 

 as in P. atlanticum, the endostyle, and consequently the germinative 

 point, are turned in the direction of the closed extremity. It follows 

 that an animal placed at a given moment in the immediate vicinity 

 of that extremity is necessarily separated therefrom some time after- 

 wards by the three or four buds which it has directly produced, and, 

 still later, not only by these but by their derivatives. 



When we examine the closed extremities of several quite adulL 

 colonies, measuring several centimetres in length, we see that the 

 four individuals forming the terminal whorl are in one specimen 

 perfectly adult and beginning to breed, in another young and still 

 furnished with an elaeoblast, elsewhere, again, in the condition of 

 simple buds, forming part of the stolon, and not yet detached from 

 the parent. In a word, the terminal whorl of one colony does not 

 resemble that of another colony of the same age, which would not 

 be the case if this whorl were the primitive whorl. From these facts 

 we see that if we desire to find the four primitive individuals, it is 

 not at the closed extremity that we must seek for them, but at the 

 open extremity. They are, in fact, incessantly pushed away from 

 the former by the whole of their progeny. 



Nervous System. — On the posterior median line there exists a 

 nerve which traverses it throughout nearly its whole extent. It 

 does not originate directly from the ganglion, but from a train of 

 cells which seem to prolong the latter backwards, runs above the 

 base of the languets, and appears to act upon a bundle of muscular 

 fibres, which, passing behind the oesophagus, traverses the cloaca 

 skirting the subintestinal peritoneal lamina. 



In the four primitive ascidiozoids the two thick lateral posterior 

 nerves terminate at the two muscular cords which start from the 

 two sides of the oesophagus and run to the common cloaca. In the 

 ordinary individuals there only exists one of these muscular cords ; 

 it is median, and morphologically represents the two cords of the 

 primitive individuals ; for it receives both the nerves. 



