( 290 ) [April, 



12. ZOOLOGY, ANIMAL MORPHOLOGY, AKD 

 PHYSIOLOGY. 



Morphology. — The Structure of the Retina. — That eminent 

 observer, Professor Max Schultze, has recently published in his 

 ■ Archiv f. Mikroskop f. Anatomie,' a memoir on the Eetina, which 

 occupies more than 100 pages, and is illustrated with eight quarto 

 plates, forming by far the most complete and clear exposition of 

 the structure of this organ which has yet been published. 

 Amongst the important new facts adduced by Professor Schultze is 

 the observation that in Mammalia a very remarkable, and, as it 

 would seem, hitherto unnoticed diversity, exists, with regard to the 

 distribution of " rods " and " cones." Whilst most of our larger 

 domestic animals, especially the sheep, ox, pig, horse, and dog, 

 present an arrangement of those elements resembling that which is 

 observed in the human subject and in apes (except, of course, in 

 the absence of the macula lutea), the cones, according to the 

 author's observations, are entirely wanting in bats, the hedgehog, 

 mole, mouse, and guinea-pig. A sort of intermediate condition is 

 met with in the cat, rabbit, and rat, in which animals are found 

 either very slender true " cones," as in the cat, or merely indications 

 of them, as in the rabbit. The development of the retina and the 

 probable functions of the rods and cones are fully discussed. The 

 great value of Professor Schultze's paper lies in the fact that he 

 has not only made many new observations, but has most carefully 

 tested the conclusions and statements of previous writers ; and 

 further, has spared no pains in illustrating his text with some of 

 the most beautiful lithographs yet published. In- his researches 

 Professor Schultze has experienced the greatest advantage from the 

 use of a solution of hyperosmic acid, Os 4 , which colours nerve- 

 tissue black, without producing much effect on connective and 

 fibrous tissue. TVe most strongly urge upon microscopists the 

 importance of making further trial of so valuable a reagent. 



Entozoa of Man and Domestic Animals in Iceland. — M. H. 

 Krabbe has made some valuable investigations on this matter, in 

 pursuance of a commission from the Danish Government. He has 

 ascertained various important facts with regard to the distribution 

 of species of Taenia, Botliriocejphalus, &c, and has observed some 

 new forms. He is quite convinced that the frequency of 

 T. marginata, csenurus, and echinococcus in Iceland is owing to the 

 very vast number of sheep which the inhabitants possess, and 

 the large number of dogs which they use in herding them. It 

 appears that in Iceland there are for every hundred of inhabitants 

 four times the number of cattle which there is for every hundred 



