ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 603 



•differentiated pinnate muscular arms ; the great reduction in the size 

 and extent of the branchial sac ; the suppression of the dorsal lamina 

 and the feeble development of the endostyle and peribranchial grooves ; 

 the relatively great length and diameter of the oesophagus, and the 

 presence of a large oesophageal groove extending nearly to the anterior 

 end of the dorsal side of the branchial sac. 



Dr. Bourne suggests that Oligotrcma psammites is an Ascidian which 

 •captures and feeds on active Crustacea of large size relatively to itself, 

 such as the Amphipod (Platyscelus ?) found in the stomach. The name 

 OUgotrema refers to the fact that the branchial sac is much reduced and 

 confined to the anterior third of the body. The paper includes a useful 

 discussion of the morphological value of the different layers of the 

 Tunicate body, and a suggestion of the term " plerome " for the meso- 

 dermic tissue filling up the space between the gut and the external 

 epithelium. 



INVERTEBRATA. 



Moliusca. 

 y. Gastropoda. 



New Pteropod.* — J. Meisenheimer describes SchizdbrancMum polij- 

 ■cotylum g. et sp. n., a new gymnosomatous Pteropod from the Indian 

 Ocean. In form it recalls CI tone, but is at once distinguishable in 

 having a well-developed dorsal glandular groove. The body is elongated, 

 dilated in the middle, pointed at the hind end ; the foot has a posterior 

 median and two anterior lateral lobes ; gills are represented solely by a 

 small longitudinal skin-fold on the ventral surface of the hind end ; 

 the oesophagus has much branched "suctorial arms," radula-sac, and 

 jaw-plate. The new form seems to be a highly specialised representative 

 of the PneumonodermatidEe. 



Breeding Experiments with Sinistral Snails.f — K. Iviinkel has 

 got specimens of Helix pomaUa with left-handed shells to breed, but 

 none of the (455) offspring were sinistral. "When the development is 

 made to occur under pressure, flat forms result, which acquire the normal 

 shape when the pressure is removed. 



The author has some interesting notes on the breeding habits and 

 life-history. After awaking from the winter sleep snails take in much 

 water, increasing their weight by 40-48 p.c. Copulation occurs in 

 favourable conditions in April, especially during or after warm rain ; 

 the spiculum amoris is not essential to copulation ; in spite of copula- 

 tion some snails do not lay that summer, others may lay twice in the 

 same summer. The egg-laying occurs from the middle of June to the 

 middle of August, usually after a warm shower ; with moderate warmth 

 and moisture most of the eggs develop ; the young are hatched on the 

 25th or 2Gth day after oviposition ; they remain 8-10 clays in the earth 

 but leave it when the rain soaks in. Snails may remain lively till the 

 end of November, if the conditions of warmth, moisture, and food are 

 all favourable. 



* Zool. Anzeig., xxvi. (1903) pp. 410-2 (1 fig.). t Tom. cit., pp. 65G-64. 



