ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 301 



Tunicata. 



Sensory Reactions of Ascidia atra.— Selig Hecht {Journ. Expp,r. 

 ZooJ., 1018, 25, 261-99, 2 figs.) finds that this Ascidiau has sis negative 

 reactions to stimuli — three direct (depending on stimulation of the 

 exterior) and three crossed (depending upon a stimulation of the interior, 

 and al>olished by severing the intersiphonal ganglion). The Ascidian 

 is sensitive to tactile stimulation, especially in siphon rims and oral 

 tentacles ; to vibrations, in the lobes of the siphon rims ; to light of 

 high intensity, not in the " ocelli," but within the siphon near the oral 

 tentacles ; to temperatures above 32° C. and below 20° C. ; to large 

 changes in osmotic pressure ; to salts, acids, bases, alkaloids, and 

 anaesthetics (but not to sugars) in solution. On the whole, the animal's 

 reactions are few. J. A. T. 



Photic Sensibility of Balanoglossids. — W. J. Crozier {Journ. 

 Exper. Zooh, 1917, 24, 211-7) has experimented with Ptychodera 

 lahamensis, and finds that it is negatively photokinetic. In addition to 

 this orienting stimulus, it is shown that light has another, possibly 

 separate, effect upon these animals — namely, the inhibition of light-pro- 

 duction. The tip of the proboscis is the part most sensitive to illumina- 

 tion, but the rest of the animal's surface is likewise open to stimulation 

 by light. The collar nervous system (delaminated part) is unnecessary 

 for the co-ordinated movements of orientation, and also for the inhibi- 

 tory influence of light on the production of luminescence. J. A. T. 



INVERTEBRATA. 



Mollusca. 

 y. Crastropoda. 



Smell and Taste in Marine Snails. — Manton Copelaxd {Journ. 

 Exper. ZooJ., 1918, 25, 177-227) has studied the olfactory reactions of 

 Alectrion ohsoleta and Busycon canaUcnlatum, which move towards the 

 dilute chemical stimuli of distant food or extrude their proboscides. 

 The osphradium is an olfactory organ, but all the skin surfaces tested 

 were found to be more or less susceptible. The movements of the 

 siphon are of much importance. Both snails show positive reactions to 

 relatively strong food solutions, and are therefore gustatory. The 

 principal external receptive areas for taste stimuli appear to be the 

 tentacles, the anterior part of the foot, and the under part of the head. 

 Touch may assist in reactions to food ; the eyes do not seem to play 

 any part ; taste is effective only in the last stages of food-procurement ; 

 smell is all important. J. A. T. 



Locomotion of Gastropods. — J. M. D. Olmsted {Journ. Exper. 

 ZooL, 1917, 24, 223-36, 1 fig.) distinguishes lateral, diagonal, composite 

 and other types of locomotion in Gastropods. Cilia are the means of 

 pedal locomotion in Marginella, Haminea and Bulla. It was found 

 that Chiton and Fissurella can move backward without reversing the 



