160 SUMMARY OF CURRENT RESEARCHES RELATING TO 



marked l)y the absence of radula and ink-sac. The genus Oplstho- 

 teutlm is adapted to life on the sea-floor ; the species Opisthoteuthis 

 depressa (Ijima and Ikeda) occurs off Japanese coasts (150 metres). In 

 structure there is evidently affinity with Octopods, but, besides the 

 absence of radula and ink-sac, there are peculiarities in the highly- 

 developed fins, in the fusion of funnel and mantle, in the presence of 

 cirri, and in the structure of the male gonads. There is also marked 

 reduction of the viscero-pericardial cavity, leading to the almost com- 

 plete disappearance of the right water- vessel ; the right oviduct is absent, 

 and the cerebral ganglia are more concentrated than in Octopus. The 

 Cirroteuthidffi may be regarded, as Brock maintained, as a divergent 

 offshoot from the Octopods. 



y- Grastropoda. 



Nervous System of Gastropods.* — B. Aeberhardt has made a com- 

 parative study of the nervous system of Gastropods, with special re- 

 ference to the difficult question of asymmetry. He starts with a 

 primitive form like Pahidina, then discusses Pomatia sepfemspiralis, 

 also not greatly modified, then Cydostoma de//aiis, then the much more 

 specialised Bithiaia tentaculata, and so on to Helix and other Pulmonates. 



Odontophore of Sycotypus canaliculatus.j — J. C Herrick explains 

 the modus operandi of this Gastropod in boring through the shells of 

 oysters and clams and in rasping out their contents. The apparatus 

 is highly complex ; the mechanism of the radula was rightly com- 

 pared by Huxley to a chain-saw, with the restriction that the sawing 

 occurs only on the return draw. The relations of buccal cartilage, 

 radula, andradula-sac, with their musculature, are explained. The nerve 

 supply of these parts has also in large part been determined. 



Arterial System of Aplysia.| — M. Blatin and F. Vies give precise 

 details of the arterial system of Aplysia punctata. The heart, consisting 

 of ventricle and bulb, gives rise to an aorta in front, a visceral artery 

 behind, and a stomach artery to the left. The branches of these 

 vessels are described and clearly figured. Torsion is apparent in the 

 arterial system ; the aorta is thrown to the right of the sagittal plane, 

 as is the visceral commissure, to which it appears to be attached : the 

 pallio-pedal and cephalic branches of the right side show in their 

 earlier origins similar evidence of twisting. 



5. Liamellibranchiata. 



Giant Scallop.§ — G. A. Drew gives an account of the habits 

 structure, and development of the giant scallop {Fecten teiiuicosiatus 

 Mighels). The shell is well adapted for rapid movement. The me- 

 chanism of swimming is described. There is a large byssal gland. It 

 seems probable that one loop of the intestine has been overlooked in 

 previous dissections of scallops. The labial palps are peculiarly ruffled 

 above and below the mouth. A special arrangement makes it possible 



• MT. Nat. Ges. Bern, 1905, pp. 112-32 (18 figs.). 



t Amer. Naturalist, xl. (1906) pp. 707-37 (16 figs.). 



X Arch. Zool. Exper., Notes et Revue, No. 4, xxxv. (1906) pp. xc.-cii. (10 figs.). 



§ Studies Univ. Maine, No. 6 (1906) pp. 1-71 (17 pis.). 



I 



