1892. 



NOTES AND COMMENTS. 93 



partially retained, the eye of the right side not having quite passed 

 over the top of the head, and both sides of the body being pigmented 

 {Comptes rendus Soc. Biologic, Jan. 16, 1892). The Professor concludes 

 that the coloration of the upper exposed side in the flat-fishes is 

 due to the direct action of the light, and arrives at some other 

 interesting results which we hope to notice on a future occasion. 



For some years Dr. R. Blanchard (of 32 Rue du Luxembourg, 

 Paris) has been occupied with the preparation of a Monograph of the 

 Hivndinea. He has now almost completed the section on Gnatho- 

 bdellidae, and appeals for the help of naturalists and museums who 

 can supply him with leeches of which the respective habitats are 

 definitely known. 



The interesting new Crinoid from the Galapagos Islands, 

 Calamocvinus diomeda:, has at last been fully described by Professor 

 Alexander Agassiz {Metn. Miis. Comp. Zool. H award, vol. xvii., No. 2, 

 1892). The monograph, which has just arrived in England, enters 

 very minutely into the structure of the skeletal system of this form, 

 and also contains notes on the apical system and the homologies of 

 Echinoderms generally. There are thirty-two plates, and rarely has 

 any Crinoid had its hard parts so magnificently illustrated. Since, 

 however, the author has given no diagnosis, no succinct description, 

 and no synopsis of its relations to other genera, we must defer a fuller 

 account of this remarkable form until we have digested the large 

 mass of facts now published. 



A STUDY of the nervous system of organisms so lowly in the 

 scale of animal life as the Alcyonarian polypes {e.g., the common 

 " Dead-men's fingers " of our British coasts) presents many features 

 of interest, and has just been undertaken by Dr. S. J. Hickson. At 

 the meeting of the Cambridge Philosophical Society on February 22, 

 Dr. Hickson communicated some preliminary results of his researches. 

 In fresh specimens oi Alcyonimn stained with osmic acid, a plexus of 

 very fine nerve-like fibrils, connected with a number of minute uni-, 

 bi-, or tri-polar ganghon-cells, could be distinctly recognised in the 

 dense, transparent gelatinous material between the several polypes of 

 the colony. In their normal state the polypes of the ^/cj^o/zmw; con- 

 tract regularly twice every twenty-four hours ; and even when the 

 colony is removed to an aquarium, where there are no tides, the 

 regularity of the periods of contraction and expansion continues for 

 two or three days. After such a period in an aquarium the polypes 

 begin to remain expanded or contract only irregularly ; but a new 

 rhythm may be easily induced by subjecting the Alcyoniiim to the 

 action of an artificial tide of any .given duration. There is much 

 analogy between this phenomenon and the opening and closing of 

 flowers. 



