ZOOLOGY. 



487 



The proboscis and its adjuncts in the nemertiues, as compared with 

 the parts of the rhabdocoeles, is explained in the following terms : 



(J. R. M. S. (2), V, pp. 811-813.) 



Conodonts. 



Nature of conodonts. — The peculiar small tooth-like organisms found in 

 paleozoic rocks, and which have been named conodonts, have been again 

 subjected to investigation by K. von Zittel and J. V. Kohon. These 

 little bodies have been regarded, at least by some old authors, as the 

 remains of vertebrates related to the myzonts or lampreys and hags. It 

 18 not probable that this view is now entertained by any competent to 

 have an opinion, but the nature of conodonts is still undetermined. The 

 authors just referred to conclude that the structures in question are 

 neither related to the dentine teeth of true fishes or selachians, the 

 horny teeth of cyclostomes or marsipobranchiates, the teeth of mollusks, 

 the beaks of cephalopods, nor the spines of crustaceans, but do in form 

 and structure closely resemble the oral armature of annelids or gephy- 

 reans. This view has been previously enunciated, but the corroborative 

 testimony afforded by independent observers is of interest. It is well 

 added that if the view thus entertained be true, " there must have been 

 in paleozoic times an immense number of very varied worm forms." 

 (S.-B. k.-bayer. Akad. Wiss. Miinchen, 1886, pp. 108-13G, 2 pi.; J. R. M. 

 S. (2), VI, p. 984.) 



Platy helminths. 



Origin of the nervous system of the nemertlne icorms. — The morphology 

 of the ueinertiue worms has been investigated by Prof. A. A. W. Hu- 

 brecht. The information respecting the origination and development 

 of the nervous system is of special interest. " No portion of the central 

 nervous system" of the chief species examined, Lineus obscurits, "takes 

 its origin from either primary or secondary epiblast, but the whole 

 nervous system is of mesoblastic origin. At first the archenteron com- 

 municates with the enteron by a wide blastophore, but later on the 

 cavity of that portion of the intestine which grows backwards is closed 

 anteriorly, and in front of this another portion of the embryonic intes- 

 tine constantly remains in open communication with the exterior ; the 



