412 SUMMARY OF CURRENT RESEARCHES RELATING TO 



running far forward to beside the oesophagus ; the peculiar twists of the 

 oesophagus; aud the hints of buccal and oesophageal pouches. The 

 nervous system is almost identical with that of PL qunyana, but a more 

 complete study of it has been made. The following points are em- 

 phasised : — (a) The absence of differentiated pallial ganglia, and the 

 concrescence of pedal and pallial cords, as in Chitonidae ; (b) the origin 

 of the visceral commissure on the corebro-pallial connectives, and not, as 

 in other Diotocardia, on the ganglionated pallial cords ; (o) the develop- 

 ment of a very large ganglion at the origin of the osphradial cord, 

 representing in part the point of origin of the pallial nerves; (d) the 

 very feeble development of the secondary pallial nerves ; and (e) the 

 strong development of the primary pallial nerves. 



Spawning and Oviposition in Trochus.* — A. Robert points out that 

 agglomerated spawn is formed by Tr. granulatus Born., Tr. striatus L., 

 Tr. conuloides Lam., Tr. exasperatus Penn. ; while Tr. magus L., Tr. 

 cinerarus L., Tr. crassus Pult. lay their eggs singly. In the former 

 series there is in the females an ampulla-like swelling on the excretory 

 canal of the right kidney, and this secretes the mucus of the spawn- 

 masses. 



Arthropoda. 



a. Insecta. 



Constancy of Insects in their Visits to Flowers, f— Prof. F. Plateau 

 has made some experiments bearing on this, following in so doing the 

 work of Prof. A. W. Bennett, R. Miller Christy, G. W. Bulman, and 

 G. W. Ord, whose results are duly acknowledged. 



(1) None of ihe Apidae observed — Bombus, Apis, Megachilc, Anthidium, 

 Coel'wxys — exhibit absolute constancy. Even those which are habitually 

 most constant may turn from the kind of plant they have been visiting, 

 and tackle a quite different species. 



(2) The species of Bombus are very fickle, rarely remaining constant 

 to one species except for a short time. 



(3) In Anthidium manicatum and Apis niellifica the constancy is re- 

 markable, but with distinct exceptions. 



(4) Like his predecessors, Plateau found that the inconstant bees 

 jiass from one flower to another quite different in colour and form ; they 

 seem indifferent except to nectar and pollen. 



(5) The difference in habit between the constant and inconstant 

 forms does not seem to imply great intelligence ; it is perhaps an ex- 

 pression of the fact that the constant forms are less strong and save 

 their energy by uniformity of action. 



(6) The constancy results in greater adeptuess in collecting the 

 nectar and pollen, and saves time, but it is not adhered to in order to 

 secure these ends. 



Periodic Poecilandry. % — P. Lesne calls attention to variational 

 peculiarities among the males of beetles belonging to the xylophagous 

 family Bostrychidae. In Bostrychopsis, Schistocercos, and Heterobostrychus, 



* Comptos Rfmlus, exxxii. (1901) pp. 850-1. 



t Ann. Soc. Entomol. Belg., xlv. (1901) pp. 56-S3. 



X Comptos Rendus, exxxii. (1901) pp. 847-50. 



