488 RECORD OF SCIENCE FOR 1886. 



anterior forcgiit opens by a crescentic slit, aud this would seem to be- 

 come the mouth of the adult; in other words, there is no epiblastic 

 stomodoeum ; part of the foregut becomes the oesophagus, and the rest 

 appears to be converted into the nephridal system. The nephridia 

 seem to long remain in a more or less eriibriouic phase, but their history 

 is very difficult to make out, and is as yet only incompletely known. 



" The mesoblast cells, once freely moving about in the blastocoel, 

 soon accumulate against the inner surface of the plates of secondary 

 epiblast, and the mass increases in size. The [irocess of differentiation 

 leads to the appearance of muscle and nerve cells at a ver\'^ early date ; 

 the mesoblast cells form a massive group in the prostomium, and a com- 

 paratively thin cell-sheet in the rest of the body. 



" Unexpected as is the mesoblastic origin of the nervous system, there 

 appears to be no doubt about it. Hubrecht, indeed, thinks that Salen- 

 sky's figures of Amphiporus viriparus point to the mesoblastic origin of 

 the nervous system in that animal rather than the mode of origin ap- 

 proved by Salensky." (Quart. Journ. Micr. Soc, xxvi, pp. 417-448, 1 pi.; 

 J. E. M. S. (2), VI, 0, pp. 614, 015.) 



Cephalic 2>its of nemertlnes. — On the surface of the heads of nemer- 

 tine worms are developed certain pits whose functions aud nature have 

 been long unknown. It has been recently suggested by M. Remy de 

 Saint Loup that the cephalic pits maybe "strictly compared to the 

 essential forms of the segmental organs" of the leeches, from which 

 they only vary in structure and function" (sic!) It is also suggested 

 that "they may serve as auditory- organs, as an irrigating and respira- 

 tory apparatus, or as a heail-kidney." (Comptes Eendus Acad. Sc, cii, 

 pp. 1576-1578; J. E. M. S. (2), Vi, p. 797.) 



Nematelminths. 



Relations of hair-worms. — The elongated hair-like animals which are 

 generally believed by common people to be vivified horsehairs — the 

 Cor^ZutZtc of naturalists — have been investigated by Prof. F. Vejdovsk3\ 

 As the result of his investigation the professor concluded that " although 

 the external form of the body appears to ally the Gordiidic with the nema- 

 toid worms, the rest of their organization is so different that they ought 

 to be separated from that class of nemotohelminths, and brought into 

 closer relations with the Annulata; the presence of a true coelom and 

 of mesenteries, as well as the highly developed central nervous system 

 and the segmental arrangement of their glands, demand this change." 

 The absence of the enteric fibrous layer to the enteric canal, in which 

 the Gordiidaj resemble the nematoid worms, " may be explained by the 

 fact that the Gordiidjie take in no food during their free-living stages, 

 while the conditions of these parts are unknown in the younger and 

 parasitic stages. As in the Annulata, the mesenteries arise by the dif- 

 ferentiation of the epithelial layer of the ccelom." 



