,85.. NOTES AND COMMENTS. 245 



We may add that partly analogous results have lately been 

 obtained by Mr. G. A. Boulenger in the study of the tadpoles of 

 frogs and toads (Proc. Zool. Soc, i8gi, pp. 593-627). The tadpoles 

 of one and the same species found in different ponds often vary much 

 in size and coloration, and in some other characters, whereas the 

 adults evolved from these tadpoles exhibit no corresponding dif- 

 ferences. The subject thus opened up is one of very wide import, 

 and the appearance of Messrs. Brooks and Herrick's completed 

 work in the Memoirs of the National Academy of Sciences will be 

 anxiously awaited, both by zoologists and palaeontologists. 



The Mollusca of the Red Sea. 



From its geographical position, the Red Sea exhibits features of 

 perennial interest to biologists, and the new account of its molluscan 

 fauna appearing in the last number of the Annates des Sciences 

 Naturelles (vol. xii., pp. 343-363, 1892) is a welcome contribution to 

 the literature of the subject. Dr. Jousseaume, the author of this 

 memoir, has made extensive explorations in the Red Sea, with the 

 result that he is able to add 200 species to the list of 800 species of 

 mollusca already recorded by previous observers. He has also 

 discovered a new species of Cistella which is the first Brachiopod 

 obtained from the Red Sea. Dr. Jousseaume supports the belief that 

 the molluscan fauna of this area presents no close affinities with that 

 of the Mediterranean ; and he believes that the species stated by 

 some previous observers to be common to these two basins have been 

 recorded by mistake. He especially instances the use of Mediter- 

 ranean sponges at Suez, and shows how some of the shells supposed 

 to occur here have been brought with these articles of commerce. 

 The Red Sea is, indeed, as Mr. Edgar Smith pointed out last year 

 {Proc. Zool. Soc, June 16, 1891), to be regarded as a large gulf of the 

 Indian Ocean. 



The great value of Dr. Jousseaume's work, however, lies in the 

 attention he has given to the variation of some of the commoner 

 species of the mollusca in accordance with their surroundings. He 

 finds that certain forms are absolutely stable, whatever be the nature 

 of their environment ; variations being confined exclusively to 

 differences in the intensity of the coloration. On the other hand, 

 there are many species that appear to exhibit almost as many 

 varieties as can be observed in any species of domestic animals. 

 These " modify their forms, vary their colour, multiply or simplify 

 their ornaments " according to circumstances. At the same time, Dr. 

 Jousseaume is a firm believer in the reality of " species," and his 

 observations on this point are worthy of special quotation : — 



" However great may be the variations I have observed in the 

 different individuals, they have always appeared to me to be confined 

 within certain limits for each species — limits which could not be 



