BRANCHIAL SENSE ORGANS OP ICHTHYOPSIDA. 207 



and arises simply from the necessity of extension and increase of the 

 branchial sense organs, with which it is solely concerned, the ventral 

 branch as such being probably solely concerned with the innervation of 

 the gill-clefts. 



A few words may be devoted to the researches of Bodenstein 1 and 

 Solger, 2 which have led to the conclusion that in the sense organs of 

 the lateral line in Teleostei nerve strands connecting the various sense 

 organs together are present. From the account of the development 

 given here such a connection might be expected to occur, for I have 

 shown that the " lateral line " has arisen solely by the extension and 

 multiplication of the primitive branchial sense organs of the vagus : 

 these are, as we have seen, connected in development, being formed 

 from one continuous sensory rudiment, and as they form one physio- 

 logical whole, we could expect a connection in the adult. Although I 

 have not attempted here to give an account of the development of the 

 "lateral line" in Teleostei, I may perhaps be allowed a few words on 

 it, as it seems to confirm the researches under discussion. 



In this case in the growth backwards of the sensory rudiment there 

 are found thicker portions, which are segmental, and thinner portions 

 connecting them. The nerve is split off along the whole length, just 

 as in Elasmobranchs. The thicker portions give rise to the sense 

 organs, the thinner portions only to nerve structures, and probably to 

 those connecting strands described by Bodenstein and Solger. 



Remains op Branchial Sense Organs in Higher Vertebrates. 



Prof. Froriep's paper, leaving aside the small error just mentioned, 

 is a very interesting and very important addition to our knowledge of 

 the ancestry of Mammalia. It is mainly concerned with the descrip- 

 tion of rudiments of these branchial sense organs of the facial, glosso- 

 pharyngeal, and vagus in Mammalia, viz. cow and sheep embryos. 

 These rudiments are only found in certain stages, and disappear later. 

 When they still exist the corresponding ganglia of these cranial nerves, 

 viz. the ganglia of facial, glossopharyngeal, and vagus, are fused with 

 the skin ; indeed, the conditions seem to be much the same as in 

 Elasmobranchii. That the ganglia are wholly or partly derived from 

 the skin in Mammalia, Prof. Froriep hesitates to decide. It is some- 



1 Bodenstein, E., "Der Seitencanal von Cottus Gobio," 'Zeit. f. wiss. Zool.,' Bel. xxxvii, 

 Heft 1, 



a Solger," Ueber die Seitenorganen Ketten der Fisehe," 'Zool. Anzeig.,' 1882, No. 127, 

 p 660 



