668 SUMMARY OF CURRENT RESEARCHES RELATING TO 



chemical substances. An example is afforded by the swarm-spores of 

 Saprolegnia, which soon come to rest under the influence of chemical 

 irritation (chemotaxis), but, when not under this influence, continue 

 their motion for a longer time. Apaerotaxis is the term given to a 

 repugnance to oxygen, an instance of which is adduced in a species 

 of Amylobacter. The same organism and Bacillus Solmsii exhibit 

 proschemot axis (positive chemotaxis) towards ether. 



The cheinotactic sensitiveness of an organism towards different 

 chemical substances appears to depend on different properties of the 

 protoplasm. While in the chemotactic movement of spermatozoids, the 

 capillary opening exercises a directing influence on their motion ; bac- 

 teria, on the other hand, display simply a swarming movement round 

 the opening. A distinction is drawn between strophic and apobatic 

 chemotaxis, the motion consisting in the former case of a twisting, in 

 the latter of a repulsive movement. Osmotaxis is distinguished from 

 chemotaxis in that it is induced, not by the chemical composition, but 

 by the osmotic property of the medium. 



Finally, the author calls attention to the inconstancy or fickleness of 

 the tactic sensitiveness of micro-organisms. They appear to be most 

 sensitive when first operated upon, and gradually to lose this sensitive- 

 ness, possibly from long cultivation diminishing the struggle for exis- 

 tence. 



Senso-motory Apparatus of the Tendrils of Cucurbitaceae.*— Prof. 

 A. Borzi has studied the anatomy of the senso-motory apparatus in 

 tendrils, which he finds to be uniform in its main features throughout 

 the Cucurbitaceas. The activity of the tendril cannot be accounted for 

 by variations in the ordinary processes of growth ; they must be attri- 

 buted to a special activity of the protoplasm. 



The phenomena may be regarded as extending over three phases : — 

 (1) Attachment to the support by means of the free extremity, and its 

 circumnutation in space ; (2) coiling round the support by the apical 

 portion ; (3) definite attachment of the whole of the tendril to the 

 support. In the first phase the apex is composed of a resistant some- 

 what horny refringent substance, with a very strongly thickened 

 cuticle. The hooked form of the apex, caused by a slight difference in 

 the growth of the two sides, serves to assist the attachment to the sup- 

 port ; the motion being the result of the negative geotropism of the 

 branch, and of the circumnutation of its apex. During the second 

 phase, the sensitive properties of the tendril come strongly into play ; 

 these are confined to its inner or concave side. During this phase all 

 the epidermal protoplasts of a tendril (except those of the basal portion) 

 must be regarded as sense-organs, and are furnished with strongly 

 contractile threads of protoplasm which are the motory organs. Every 

 sensory cell possesses a number of very short protoplasmic papillas, 

 which constitute a tactile body. In the third phase, the tendril has 

 acquired a somewhat woody consistency and great elasticity. It becomes 

 closely attached to the support. 



The permanence of the position induced by the elasticity of the 

 protoplasmic threads, and the sensitive phenomena in general, are 



* Atti R. Accad. Liucei, x. (1901) pp. 395-400. 



