MUSEUM OF COMPARATIVE ZOOLOGY. 335 



As the tube grows, these organs lengthen also, and soon a single 

 row of germinative vesicles is seen extending along each of them (Fig. 

 28) ; they are therefore the ovaries. At the time that the constric- 

 tions, which arc the first indications of the zooids, appear in the 

 outer wall of the tube, each ovary is seen to be made up of a row of 

 eggs, equal in number to the constrictions ; and as the zooids are 

 developed, and their body cavities are separated from the sinus cham- 

 bers of the tube, the chain of ova also divides, so that a single eg^ 

 passes into the body cavity of each zooid (Figs. 29 to 34, s) and 

 becomes suspended there by a gubernaculum, by means of which it is 

 attached to the wall of the branchial sac, as already described. 



Since the chain-salpa, at birth, always contains a single unimpreg- 

 nated egg, organically connected with its body, and since this egg and 

 the resulting embryo are nourished by the blood of the chain-salpa, 

 by means of a true placenta, and since no reproductive organs have 

 hitherto been described in the solitary Salpa,* it seems most natural 



Fig. 33. 

 h. 



<N. 



1- 



Side view of a single zooid from a chain at the stage shown in Fig. 34 ; the neural side is upper- 

 most : b, outer tunic ; d, wall of atrial chamber ; /, respiratory muscles ; /', muscles of bran- 

 chial aperture ; /", muscles of atrial aperture ; g, atrial aperture ; h, cavity of branchial sac ; 

 i, cavity of atrium ; k, peripharyngeal ridge ; I, epipharyngeal folds ; in, endostyle ; n, gill ; o, 

 mouth; o", stomach ; o''', intestine; o'"', anus j r, heart; s, egg ; t, testis ; v, ganglion ; v,\ 

 languette. 



* Although I made my observations without any knowledge that the origin of 

 the eggs within the solitary Salpa had ever been traced, I cannot claim original- 

 ity for the observation ; since Kowalevsky states incidentally, in his paper upon the 

 "Development of Pyrosoma," that this is the case in Salpa. He gives no description 

 or figures, and confines himself to a bare statement of the fact, which occupies not 

 quite one line. The passage containing the reference will be quoted farther on. 



My observations were made in August and September, 1875, and Kowalevsky's paper 

 on Pyrosoma was printed in August, 1875, and readied the library of the Boston 

 Society, where I first saw it, on October 11. 



