Miscellayieous. 95 



to these segmental organs. In his so-called 'Comparative Anatomy' 

 he speaks of the possibility of a compiirison of the oviducts and 

 tubae to the segmental organs of the Vermes. This is completely 

 refuted by the observations here given : the true segmental organs 

 of the Vertebrata (hitherto detected only in the Selachia) have 

 nothing to do with the tu])a^ and the oviduct ; the former originates 

 from the primitive renal duct, and the latter is produced by a fold 

 M-hich finally leads to the formation of a tiibe ; the tuba? are only 

 the permanently open orifices of the primitive renal groove, and 

 they consequently originate in quite a different manner from the 

 true segmental funnels. 



The comparison here made leads to far-reaching consequences. 

 Assuming it to be correct, it follows that the Annelida are more 

 nearly allied than the Ascidia to the Selachia, and therefore also to 

 the Vertebrata in general (with the exception of ^im/)7H'o.r»s). It 

 might be objected that the spinal cord and the chorda are of more 

 importance for the recognition of relationship than the primitive 

 kidney and the segmentation of the body, so that the Ascidia are 

 more nearly allied than the Vermes to the Vertebrata. But this 

 objection is partly refuted by the circumstance that according to 

 Kowalevsky's investigations the ventral cord of the Vermes and 

 Insecta is formed in a perfectly analogous manner to the dorsal cord 

 of the Vertebrata. The chorda alone seems to offer any difRcultv ; 

 but it is still questionable whether the chorda of the Ascidia is 

 really to be compared so nnconditionally to that of the Verte- 

 brata ; and, on the other hand, Kowalevsky, in his ' Embryological 

 Researches on "Worms and Insects,' even indicated as a chorda a 

 fibrous cord discovered by Leydig in the earthworm and detected by 

 Claparede in numerous worms, and which in its origin and position 

 between the ventral cord and the intestine exactly resembles the 

 chorda of the Vertebrata. Xevertheless the histological structure of 

 this cord is essentially different. 



If the embryo of an annelide be turned so that its ventral surface 

 lies upwards, its section presents exactly the same arrangement of 

 the organs as in the Selachian embryo. Consequently, by the dis- 

 covery of the segmental organs, the belly of the annulose animal is 

 identified with the back of the vertebrate. This is not the place to 

 trace this conception to its further consequences ; in this respect, as 

 also with regard to the detailed pi-oof of the facts given above, 

 reference must be made to a more complete memoir which will appear 

 shortly in the second volume of the 'Arbeiten aus dem zoologisch- 

 zootomischen Institut in Wiirzburg.' — Centralbh fur die med. Wis- 

 sensch. 1874, No. 35. 



Wiirzburg, July 1874. 



Segmental Organs in adult Selachia. By C. Semper. 



I can now follow up my former preliminary communication on 

 the occurrence of segmental organs in Selachian embryos with a 

 further statement that such organs may also be very easily detected 

 even in adult animals, but only in fresh or very well-preserved 



