ZOOLOGY AND BOTANY, MICROSCOPY, ETC. Ill 



of certain types of nerve-cells in the brains of white mice. Filamentous 

 mitochondria are commonest, hut there are also rod-like, granular, and 

 block-like forms. There is also, in the majority of cases, a variation in 

 the form of mitochondria in the same cell. They are usually more 

 granular near the nucleus than peripherally ; they are invariably rod- 

 like or filamentous in the processes. They occur not only between the 

 Nissl bodies (as is generally believed), Jiut also embedded in them. In 

 different kinds of nerve-cells the mitochondria differ microchemically ; 

 thus in some cases they are more resistant than in other cases to fluids 

 containing acetic acid. 



"^o 



Text-book of Histolog'y.*— H. E. Jordan and J. S. Ferguson have 

 prepared a text-book of histology which aims at relating the facts of 

 structure to those of function, and at illustrating the generalizations 

 which unify the whole subject. The minute structure of all the systems 

 is described, and there is a long chapter on technique. 



c- General. 



Structure of Feathers and their Taxonomic Significance.f — ^Asa 

 0. Chandler has enquired into the taxonomic value of peculiarities in 

 feathers. A detailed account is given of a typical feather. Under 

 ])lumules are discussed unspecialized plumules, powder-down, oil-gland 

 feathers, and nestling feathers. Filoplumes are then discussed and the 

 various kinds of contour feathers — remiges, rectrices, unspecialized 

 contour feathers, ornamental plumes, ear coverts, facial bristles and 

 eyelashes, and facial ruffs. In connexion with colour, particular attention 

 is paid to "isotely" or the attainment of a similar result in different 

 ways. An iriteresting point is that when pigment is absent in albinos, 

 the structural specialization so frequently involved in the production of 

 colour effect is also absent. 



The author gives an account of the peculiarities of feather-structure 

 in the various orders and sub-orders of birds — a big undertaking. It 

 appears that the structure of the feathers has great taxonomic value, 

 much more than scales on fishes or hair on mammals. Importance 

 attaches especially to the aftershaft, the rami, the distal barbules of the 

 remiges, and the degree and manner of simplification of the barbules 

 of the body-feathers. A study of the minute structure of feathers is 

 shown to be of very striking corroboratory value in reference to conclu- 

 sions as to the relationships of orders, and a phylogenetic tree is 

 submitted. 



Evolution of Lizards.^ — G. A. Boulenger discusses the lines of 

 evolution which have led from Lacerta and Nucras, occurring in 

 Oligocene and Miocene, to derivative genera like Latastia,AcanthodactyluSy 



* A Text-Book of Histologj'. New York : (1916) 800 pp. (594 figs.). See also 

 Trans. Amer. Micr. Soc, xxxv. (1916) pp. 159-60. 



t Univ. California Publications (Zool.) xiii. (1916) pp. 243-416 (25 pis. and 



V figs.). 



X Trans. Zool. Soc.,xxi. (1916) pp. 1-104 (7 pis. and 12 figs.). 



