ANATOMY AND PHYSIOLOGY OF SALPA AND PYROSOMA 49 



It thence appears that the other half of Chamisso's theory is also 

 perfectly true, viz., the aggregate form of Salpa (Salpa W) produces the 

 solitary form {Salpa A), and the circulator}- s}-stem of the foetus in 

 this case is connected with that of the parent, not iimnediately , but by 

 means of a very distinct and well-developed placenta. 



Here is one very clear distinction between the two processes of re- 

 production. Are there any other differences ? To answer this ques- 

 tion we must proceed to trace back both processes to their origin. 



32. It has been seen that the young Salpce B are developed by a 

 process of gemmation from the gemmiferous tube of Salpa A. 

 Whence comes the tube itself? 



The smaller the individual of the form A examined, the shorter is 

 the gemmiferous tube, and the less developed the buds upon it. In 

 individuals just free, or about to be free, it is a very short cylindrical 

 tube, arising on the right side and just in front of the heart, and 

 curving downwards and backwards, Plate XVI. [Plate 6] figs. 3, 3 a. 



In still smaller attached specimens it appears as a very short, some- 

 what conical process (imperfectly divided by a partition) of the dorsal 

 sinus, 'close to the heart ; its walls are smooth, and the blood-cor- 

 puscles are easily seen passing up one side and down the other of the 

 partition, Plate XVI. [Plate 6] fig. 4. 



It is clear, therefore, that the gemmiferous tube is nothing more 

 than a stolon, containing a diverticulum of the circulatory system 

 of the parent, and the whole process of reproduction as it is mani- 

 fested in Salpa A is one of gemmation. Salpa B is a bud of Salpa A. 



33. Following the same course of investigation with regard to the 

 young Salpa A (which it has been seen is produced from Salpa B), it 

 is found, that in Salpcs B, which are either still adherent to the gem- 

 miferous tube or just set free, there is no protuberance of the inner 

 tunic into the respiratory cavity ; but where this afterwards exists, 

 a pedicle of greater or less length is attached, and running backwards, 

 carries at its extremity an oval cellular mass, Plate XVI. [Plate 6] 

 fig. 8. This hangs suspended by its pedicle in the cavity of the sinus, 

 and is freely bathed by the blood. In one specimen the length of 

 the pedicle was oJuth of an inch, the long diameter of the oval body 

 about f,^o^h. of an inch. 



In still younger forms of the Salpa B, and indeed as soon as the 

 separate organs are distinguishable, the outer tunic bulges slightly in 

 the middle line behind the outline of the posterior aperture and 

 beneath the nucleus, Plate XVI. [Plate 6] figs, i, 2 ; this protuberance 

 is caused by the presence of a spherical body {q) about xoVoth of an 

 inch in diameter, containing a clear vesicle xrVoth of an inch in 

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