ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 191 



c General. 



Atavism.* — M. Hilzheimer thinks that biologists have been too 

 easy-going in the use of the word and concept " atavism." He maintains 

 that although atavisms occur, we cannot give this interpretation to 

 supernumerary fingers and toes, nor to zebroid stripes in horses, and so 

 forth. It is interesting to notice that atavisms in domestic animals are 

 clearest in those which have had a monophyletic origin, but have been 

 separated by isolation into numerous races. In intercrossing of these 

 races the isolated primordia come together again. In polyphyletic races 

 it is extremely improbable that there could be an atavism harking back 

 for a considerable number of generations. 



&* 



Interesting Structural Analogy.f — Austin Hobart Clark points out 

 the resemblance between the " snow-shoes " of the ruffed grouse (Bonasa 

 umbellata) and the supplementary plates in Crinoid arms. The " snow- 

 shoes " which develop in winter are formed from two rows of " scutes " 

 on either side of each toe, which increase the area of the foot by as 

 much again. "Thus a bird walking about in the winter brings to bear 

 only half as much weight in any given spot as the same bird in summer, 

 and is thereby enabled to tread securely upon slightly compacted snow." 



In Crinoids the food consists of small organisms which fall on the 

 upturned and outstretched arms and pinnules, and are thence conducted 

 by a ciliated " ambulacral groove " to the mouth. The increase of area 

 by two rows of supplementary plates on each side of the median row is 

 very advantageous. The development of accessory side-plates occurs in 

 the Crinoids of deeper waters, where the food consists mainly of dead 

 organisms. They are suppressed or absent in littoral and pelagic forms, 

 whose food consists of minute living animals. 



■■-> 



Osmotic Growths.^ — Stephane Leduc regards Biology as a depart- 

 ment of the physico-chemistry of fluids. With gelatin and drops of 

 potassium ferrocyanide one can make nucleated artificial cells which 

 " die " after a time, and by dropping fragments of salt into appropriate 

 solutions one can get osmotic growths like polyps and periwinkles, 

 mushrooms and moulds, corals and leaves. Of course, osmotic phe- 

 nomena are important in organisms, and require much more study than 

 they have as yet received, but Leduc's osmotic growths do not afford 

 what the title of his book suggests. 



Male Genital Organs in Insectivora and Lemuridae.§ — "W. Kaudern 

 has made a comparative study of the male genitalia in these two orders, 

 and some of his results throw light on systematic relationships. It 

 appears, for instance, that the Chrysochloridae are more primitive than 

 other Insectivora, and the Tupajidse more specia'ized. It is shown that 

 as regards the penial structure the Lemuridse exhibit two divergent 

 types, derivable however from a common stock — that of the Madagascar 

 Lemurs, and that of the Lemurs on the African continent and in Asia. 



* Zeitschr. iudukt. Abstammungslohre, iii. (1910) pp. 201-14. 

 t Ann. Nat. Hist., v. (1910) pp. 358-61 (2 figs.). 



X Theorie physico-chimique do la Vie et Generations spontanees, Paris, 1910, 

 202 pp. (57 figs.). § Zool. Jahrb., xxxi. (1910) pp. 1-106 (46 figs.). 



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