213 



servations and those of Kowalevsky are correct, but Sal en sky 

 soon afterwards published three very complete and thorough papers on 

 Scclpa [Zeitschx. f. wiss. Zool. XXVII. Bd. p. 179—237; Morpholog. 

 Jahrbuch, III. Bd. 4. Heft; and Zeitschr. f. wiss. Zool. XXX. Bd. 

 p. 275 — 293), and in these he says that Kowalevsky and I are wrong 

 in the statement that the eggs do originate, as eggs, in the solitary 

 Salpa. He acknowledges that the eggs can be traced back to a mass 

 of cells at the base of the stolon, but he claims that they do not become 

 eggs until they pass into the bodies of the chain Salpae ; that what I 

 have called an ovary is not an ovary at all, but simply a mass of un- 

 differentiated embryonic cells which gives rise to the ovaries of the 

 chain- salpae, and also to their digestive organs. He therefore regards 

 the solitary Salpa as the sexless, and the chain-salpa as the hermaphro- 

 dite sexual form, and holds that we do have in Salpa an instance of 

 true alternation. 



The U. S. First Commission, under Prof. Baird, collected and 

 preserved, for me, last summer an abundant supply of specimens of a 

 very large undescribed species of Salpa, and as they proved to be in ex- 

 cellent condition for microscopic work, I have employed myself this 

 winter, with the assistence of Dr. J. Ber mann of Baltimore, in 

 studying the development of the Salpa chain, by means of sections. I 

 have verified most of the points in Salensky's account, and find that 

 the general anatomy of the stolon, as seen in transverse sections is 

 about as he describes it , although there are many features which he 

 has overlooked. Upon cutting longitudinal sections of a very young 

 stolon we found that it is very much more complicated that the trans- 

 verse sections seem to indicate, and that Salensky's account is 

 therefore very imperfect. A transverse section at the stage shown in 

 his figure 12 (Knospung der Salpen) looks very much like his figure, 

 but a longitudinal section at the same stage shows that the mass of 

 cells which is marked Ms. in his figure 12, is not a mass of mesoderm 

 at all, but a series of digestive cavities, arranged as a row of flat ver- 

 tical parallel pouches, opening into the central tube of the stolon, the 

 Athemrohr of Salensky, and apparently the Darmrohr of Kowa- 

 levsky. The walls of these pouches are continuous, at their inner 

 edges with the lateral walls of the »Athemrohr«, and their outer sur- 

 faces are separated from each other by infoldings of the ectoderm ; the 

 first traces of the constrictions between the chain-salpae. The digestive 

 cavities of the chain-salpae are therefore formed as we should expect 

 from the analogy of other Tunicates, and the »Endoderm« of Salensky 

 has nothing to do with them. 



Now as to the microscopic structure and the history of Salensky's 



