ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 49 



Spire Variation in Pyramidula alternata.* — F.C. Baker has tried 

 to ascertain the amount of variation in the spire of this species from 

 several localities. One of the most noticeable features in the curves 

 submitted is their tendency to assume a multimodal form, which is 

 indicative of great variability. The Western specimens have a higher 

 shell, on the average, than the Eastern forms, and a much larger amount 

 of variation in spire elevation. 



Tidal Synchronism of Littoral Animals.t — 0. Bonn gives the 

 results of observations on Littorina and other shore animals. The peri- 

 winkle has two ways of orientating itself, one corresponding to the 

 period of maximum wetness, and the other to maximum dryness. This 

 may be seen on other shore animals, and the duration and extent vary 

 according to the habitat, whether supra-littoral zone (e.g. L. ruclis) or 

 lower down. The habit is persisted in, even in aquaria, where a shadow 

 may produce the effect. The animal takes its bearings in relation to a 

 certain direction, which the author terms the line of luminous force. 

 In other words, it is due to a light effect on more or less hydrated 

 protoplasm. 



Effect of Temperature on Growth in Physa taslei.f — M. H. Rajat 

 finds that in a brook at Saint-Clair near Lyon, there is a difference of 

 6° C. between the temperatures at its source and at its junction with 

 the Rhone. In it Physa taslei is abundant ; in the region of the lower 

 temperature they are larger both in length and diameter, and in the 

 Rhone itself, they are two-thirds larger than those at the source of the 

 brook. 



5. Lamellibranchiata. 



Variations in PectenJ — C. B. Davenport makes a comparison of 

 Pectens from the east and the west coasts of the United States. He 

 procured a large collection of Pectens from Dunedin, on the Gulf Coast. 

 15 miles west of Tampa, Florida (Pecten gibbus var. dislocatus) ; and 

 he obtained another collection from San Diego, California {Pecten 

 vmtricosus). The Tampa and San Diego Pectens appear to be closely 

 related, and environmental factors being the same, the variability 

 should be the same. Any considerable difference of variability is 

 probably due to a difference in the action of the environment. It turns 

 out that in all proportions measured, the San Diego Pectens show 

 themselves from 50 p.c. to 100 p.c. more variable than those of Tampa. 

 The conclusion arrived at is that the greater variability of the individuals 

 from San Diego is due to the more varied present environment, which 

 tends to make some shells deviate in one way and others in another, 

 and to the past rapid changes in the physiographical conditions which 

 have favoured the more responsive, adjustable individuals, and so have 

 given rise to a race of which the individuals are easily modified by the 

 diverse environments offered. The geographic history has given San 



* Amer. Nat., xxxviii. (1904) pp. f.61-8 (4 fi^s.). 

 + ( omptes Rendus, exxxix. (1904) pp. 646-S. 

 t Ann. Soc. Linu, Lyon, 1. (1904) pp. 131-:;. 

 § Mark Anniv. VoL, 1903, pp. 121-:56 (1 pi.). 



Feb. loth, 1905 v. 



