ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 509 



In giving an account of the post-embryonic development tlie author 

 deals particularly with the digestive tract, and points out the differences 

 between his account and that given by Goette, of Nereis dumeriUi, in 

 the history of which there would seem to be very considerable lacunae, 

 all the intermediate processes which would furnish the genetic con- 

 nection between the part which that author considers as the rudi- 

 ment of the digestive tube, and the tube itself, being neither 

 described nor figured. Any conclusions based on a comparison of the 

 mode of formation in these two species would be premature, and must 

 be left for future observers. 



Nervous System of Hirudinea.* — M. Saint-Loup finds that the 

 arrangements of the nervous system which were thought to be peculiar 

 to Clepsine are very common among the Hirudinea. Commencing 

 with Nephelis, where the transparency of the tissues assists in the 

 investigation, he saw that the ganglia of the ventral chain had on tlieir 

 ventral surface six capsules quite distinct and easily isolated from the 

 rest of the nervous mass. In Aulastomum similar capsules are to be 

 observed ; and the same is true of the medicinal leech. The author 

 has also been able to detect in all Hirudinea examined the intermedi- 

 ate or unpaired nerve which was found by Brandt in Hirudo, but not 

 detected by Baudelot in Clepsine. Similarities in structure are also to 

 be seen in the supra- and sub-oesophageal ganglia, and in the sub- 

 caudal mass. M. Saint-Loup hopes to be able to give a general 

 morphological account of the nervous system of the Leeches. 



Bite of the Leech. t — G. Carlet, in continuation of his previous 

 paper,t states that, as soon as the leech is fixed, its anterior portion 

 becomes sharply withdrawn, owing to the contraction of the longi- 

 tudinal muscular fibres ; this serves as a fixed point for the jaws. 

 These work quite regularly backwards and forwards, and the move- 

 ments may be registered as two per second. A preliminary phase 

 in the bite is an uprising of the skin into a small mammillated 

 process ; next we find three linear incisions, which are equidistant 

 and do not meet. Gradually they do so, and we get a triangular 

 wound, the three planes of which correspond to the three jaws. The 

 denticles of the jaws are not strong enough to produce at one blow a 

 wound which gives rise to a flow of blood. 



Continuing his observations,§ Carlet finds that the jaws of the 

 leech are the essential agents in suction and deglutition ; to effect 

 the former the jaws separate from one another and allow of the 

 entrance of the oesophagus; in deglutition the jaws approach one 

 another, and by a kind of piston-action drive the blood in the direction 

 of the stomach. 



Development of Phoronis.]] — A. Foettinger found in the morula- 

 stage of Phoronis that the cavity contained a few spherical or oval 



* Comptes Eendus, scvi. (1883) pp. 1321-2. 



t Ibid., pp. 1244-6. 



X See this Journal, ante, p. 212. 



§ Tom. cit., pp. 1489-40. 



II Arch. Biol., iii. (1882) pp. 679-86 (1 pi.). 



