ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 893 



true infundibula of Eotifers and flat-worms are never developed at all 

 in Polygordius ; the infundibula of this Annelid are, rather, homolo- 

 gous with a part of the excretory canaliculi. The comparison of the 

 transitory head-kidney of the larva of EcMurus with that of the larva 

 of Polygordius is very instructive, and the only differences lie in the 

 fact that in the former the fine canaliculi are not connected by a 

 membrane, and that these are remnants of the terminal infundibula. 

 The author hopes he has rigorously identified the corresponding parts 

 of the head- kidney in Polygordius and Echiurus with the excretory 

 apparatus of Eotifers and Platyhelminths, He states, in conclusion, 

 that his results have been independently confirmed by Dr. E. Meyer, 

 who is working at Naples. 



Nervous System of the Archiannelidse.* — J. Fraipont publishes 

 some interesting facts concerning the structure of the central and 

 peripheral nervous systems in the three genera Polygordius, Sacco' 

 cirrus, Protodrilus. 



In all the Anneliria proper, the central nervous system, though 

 originating in the ectoderm, becomes subsequently disconnected with 

 it and separated by the muscular layers of the body-wall. In Proto- 

 drilus it retains its embryonic position, and is not even separated by a 

 membrane from the circumjacent epidermis ; the cells found on the 

 lower surface of the nerve-cord are but little difierentiated and pass 

 gradually without any break into those of the epidermis. The 

 central ganglia, however, are surrounded by a special sheath, but like 

 the ventral cord lie in the epiderm itself. In Polygordius the two 

 halves of the ventral cord are united closely together as in the higher 

 Annelids, otherwise they are arranged as in Protodrilus, the cerebral 

 ganglia are divided into three regions, two antei'ior, one median, and 

 two posterior ganglia. They are covered by a delicate membrane 

 which isolates them from the epidermis within which they lie and 

 from each other. The anterior ganglia supply the tentacles and the 

 posterior the ciliated fossae. In Saccocirrus the nervous system is in 

 the same rudimentary condition ; the cerebral ganglia are more con- 

 densed and not isolated as in Polygordius. In all three genera a rich 

 nervous plexus lies within the longitudinal muscles of the body-wall, 

 which is in connection with the ventral chain as well as with certain 

 of the superficial epidermic cells. The paper terminates with a dis- 

 cussion on the origin of the nervous system in Annelids and its 

 relation to that of Chcetognatha. 



Anatomy of the Hirudinea.t — A. G. Bourne bases his memoir on 

 the study of forms belonging to ten genera. 



Under the head of external characters he addresses himself to the 

 question, How far in the series of Hirudincan genera do external 

 characters express the metamcrically segmcntcfl nature of their or- 

 ganization? He takes as an example Pontubdella muricata, and 

 describes the internal and external characters of a normal somite ; 



♦ Bull. Acad. R. ndg., viii. (1884) pp. 99-120. 



t Quart, Journ. Micr. ScL, xxiv. (1884) pp. 419-508 (11 pis.). 



