ZOOLOGY ANB BOTANY, MICROSCOPY, ETC. 431 



In degeneration tbe eye proceeds stej) by stop backwards towards 

 the brain, after first losing its accessories, such as the lens, cornea, 

 sclerotica, &c. 



In BrancMostoma lanceolatum brain as well as eye has disappeared. 

 Forms so degenerate as BrancMostoma and Ascidia should not be 

 taken as a standard on which to base conclusions for the origin of 

 the Vertebrata. 



Recognition by Marine Animals of the Hour of the Day.* — The 



changes produced by the tides are apparently much more important to 

 marine animals than those due to the rotation of the earth ; but Mr. 

 W. K. Brooks points out that many important physiological changes 

 are regulated according to the hour of the day, in these organisms as 

 well as in terrestrial animals and plants. In support of this, he 

 cites the regularity with Avhich certain forms deposit their eggs at 

 stated times of the day or night (indejiendently of the influence of 

 temperature, light, &c.), and the regularity with which certain Actinice 

 expand. The phenomena, he considers, have been established in each 

 species by natural selection on account of their advantage to the 

 organism. 



Clans' Elementary Text-book of Zoology.j— The second half of 

 Mr. A. Sedgwick's edition of Prof. Claus' text-book has been published, 

 so that the English student has now a complete handbook of zoology, 

 which is infinitely better than any which has yet appeared in this 

 country. 



B. INVERTEBRATA. 



Morphology of Suckers of Animals.| — M. J. Niemiec gives a list 

 of the very various animals which he has examined in the course 

 of his interesting study. Dealing first with the Echinodermata, he 

 comes to the following conclusions : — the sucker of Asteriscus is a 

 terminal enlargement of the ambulacral tube in which the different 

 layers undergo a more or less marked modification ; the epithelium 

 has a subcuticular differentiation, a granular mass being formed 

 which increases the resistance of the dermis ; the layer of connective 

 tissue gives rise to a ring from which muscular bundles are given 

 off in various directions ; the supplying nerve sends off circular 

 branches which unite to form a nerve-ring ; a vacuum is effected by 

 the contraction of the longitudinal and perpendicular muscles of the 

 disk ; when the sucker is about to be detached the acetabular cavity 

 disappears owing to the contraction of the lateral muscles of the disk, 

 and by the pressure of the liquid in the ambulacral tube. 



For the Cestoda, Taenia- coenurus as a type was taken, and sections 

 of the scolex, stained with borax-carmine, gave excellent results ; their 



* Science, iv. (1884) p. 429. 



t Claus,. C, ' EIemen1-aiy Text-book of Zoology.' Special Part : Mollusca to 

 Man. Translated and edited by Adam Sedgwick, M.A., with the assistance 

 of F. G. Heathcote, B.A., 352 pp., figs. 492-706. Svo, London (W. Swan 

 Sonnenschein & Co.) 1885. 



% Eec. Zool. Suisse, ii. (1885) pp. 1-148 (S-pls.). 



