ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 33 



inhibits the growth of the spurs. The male phimage and spurs are on 

 this view regarded as organs which develop out of the characters of the 

 hypothetic non-sexual embryonic form without any influence of the 

 sexual glands. " The male plumage and the spurs become male sex- 

 characters, not because they result from an action of the male sexual 

 gland on the non-sexual soma, but because the development of these 

 non-sexual characters is influenced in the female by the internal secre- 

 tion of the female sexual gland." Generalizing Pezard's suggestion, 

 Lipschutz proposes to divide the sex-characters of Vertebrates into two 

 groups : — (1) Sex-characters not dependent on the puberty glands, but 

 the outcome of the characters of the non-sexual embryonic form ; and 

 (2) sex-characters dependent on the puberty gland, which evokes them 

 by acting on the non-sexual embryonic form, either by furtherance or 

 by inhibition. 



Development of Auditory Capsule in Man.* — George L. Streeter 

 has studied this in human embryos. The changes in size and form 

 during development are accomplished in part by a progressive and in 

 part by a retrogressive differentiation of the constituent tissues. Through- 

 out the entire period of growth, as far as material was available for 

 study, it was found that the margins of the cartilaginous cavities undergo 

 a process of continual transformation. They exhibit a state of unstable 

 equilibrium, in respect to the opposing tendencies toward a deposit of 

 new cartilage on the one hand, and toward the excavation of the old on 

 the other. The margins are always either advancing or receding, and in 

 this way are produced the progressive alterations in their size, shape, 

 and position. In this manner suitable chambers are provided for the 

 enlarging membranous labyrinth. 



The general tissue-mass of the otic capsule, during the period re- 

 presented by embryos from i mm. to oO mm. in length, passes through 

 three consecutive histogenetic periods— namely, the stage of mesenchymal 

 syncytium, the stage of pre-cartilage, and the stage of true cartilage. In 

 the subsequent growth of the capsule it is found that in areas where new^ 

 cartilage is being deposited the tissues of the areas concerned follow the 

 same progressive order of development. In areas, however, where 

 cartilage previously laid down is being removed, the process is reversed. 

 The tissue in such areas returns to an earlier embryonic state, that is, it 

 u ndergoes de-differentiation. Tissue that has acquired all the histological 

 characters of true cartilage reverts to pre-cartilage, and then to a mesen- 

 chymal syncytium. In the latter form it re-differentiates into some more 

 specialized tissue — in this case for the most part into a vascular reticulum. 



The perichondrium is a derivative of the periotic reticulum, and forms 

 an outer limiting membrane along its cartilaginous margin. During the 

 foetal period the perichondrium does not rest directly against the true 

 cartilage, but is separated from it by a zone of transitional tissue con- 

 sisting partly of pre-cartilage and partly of reticulum. 



"Dislocated" Mice.f—Etienne Rabaud has studied the hereditary 

 relations in a race of mice, arising as a mutation in a normal line, 



* Amer. Journ. Anat., xxii. (1917) pp. 1-25 (12 figs.). 

 t Bull. Soc. Zool. France, xlii. (1917) pp. 87-97 (1 fig.). 



March 20th, 1918 D 



