1 882.] Zoology. 147 



lively movements. It was left for five hours until quite dry, and 

 all that could be seen of it under 350 diam., was a brown speck 

 under the cover-glass. A drop of water was allowed to run be- 

 neath the latter. Almost immediately after it had reached the 

 remains of the Tardigrade, a fine pellicle was evident, surrounding 

 the brown speck and manifesting the general outlines of the body 

 and ova. The normal wall then appeared, enclosing the contents 

 of the intestine ; the minutest details of the outer skin appeared ; 

 after twenty minutes the mouth with its fingers and tube, the jaws, 

 and the feet were fully developed. Subsequently the parts con- 

 necting the jaws with the oesophagus came into view. No move- 

 ments and no development of the ova were observed in the three 

 hours occupied by these observations. The too close apposition 

 of the cover-glass to the slide being now remedied, the animal 

 was supplied plentifully with water, but, when .searched for the 

 next day, could not be found, having probably departed in search 

 of more comfortable quarters, for the algae which had surrounded 

 it were disturbed, and neither the remains of the jaws and skin, 

 usually found after specimens have died, nor eggs, were discov- 

 ered. 



Variation in /Equorea forskalea.— Professor C. Claus, ac- 

 cording to the Journal of the Royal Microscopical Society of 

 London, while giving an account of this Adriatic medusa, takes 

 the opportunity of making some criticisms on Professor Haeckel's 

 classification of the ^Equoridae. A careful study of this form has 

 shown Claus that it is subject to extreme variation ; variations so 

 great as to have led Professor Haeckel to make a number of 

 genera and sub-genera for their reception. It is not possible to 

 abstract a critical paper of this kind, and we must be content to 

 direct attention to the following points. Claus finds that the 

 color varies with age and sex; the young may well be called 

 viirina, as Gosse called them; later on'blue pigment- granules may 

 appear in the ectoderm, and especially in the gonads of the male, 

 while the female may take on a more or less reddish coloration 

 (the A. violacea of Milne Edwards). The radial canals vary in 

 number from just over fifty to nearly eighty. The form and 

 size of the mouth-lips depend on the state of contraction of the 

 specimen, on its age, and on the breadth of its umbrella. Alto- 

 gether, according to Professor Claus. Haeckel would seem to 

 have afforded a very interesting proof of the origin of species by 

 variation. 



Development of the Sterlet.— A resume of Professor W. 

 Salensky's Russian paper on this subject appears in the Jour- 

 nal of the Royal Microscopical Society. The segmentation of 

 the egg is on the amphiblastula type; the gastrula, however, is 

 an archigastrula. In th n, and in the primitive 



formation of its mesoderm, the sterlet resembles Amphioxus, but 



