ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 19 



Lis studies of young lambs and pigs, more particularly of the former, 

 which yielded a pretty complete series of preparations, comes to the 

 following conclusions. He started from embryos 1 • 5 cm. long, which 

 as yet showed no traces of cartilage in the visceral arches or about 

 the labyrinth. 



A. 1. The proximal segment, at an early period separated from 

 the cartilage of the first visceral arch, becomes the rudimentary incus 

 (the second visceral, Eeichert's, cartilage here plays no part). 2. The 

 distal moiety of the same cartilage gives rise to Meckel's cartilage 

 (s. str.), together with the rudiment of the malleus. 



B. 1. The stapes is formed independently of the other auditory 

 ossicles. 2. It begins as an accumulation of cells around the man- 

 dibular artery, acquiring afterwards the form of a trapezoidal plate, 

 which then becomes pentagonal, and finally bell-shaped. 3. From 

 its first appearance the stapes is a perforate and not a solid plate, 

 though wrongly taken for the latter by all embryologists. 4. The 

 course of the mandibulary artery, and the way in which the stapes 

 arises round it, strikingly influences the shape of the stapedial rudi- 

 ment. The artery conditions the perforation of the stapes, also the 

 annular excavation of the anterior stapedial crus. The role thus 

 played by the mandibular artery is but provisional. Eventually the 

 artery vanishes, exceptionally persisting in a few vertebrates. 



Salensky, accordingly, reverts to the views of Eeichert. On these 

 problems the minds of English anatomists have been much exercised 

 by the well-known researches of Professors Huxley and W. K. Parker. 

 Huxley * at first supported Eeichert, and subsequently both he and 

 Parker derived the incus from the hyoid cartilage. In certain details, 

 affecting the transformations of this proximal segment of the hyoid 

 among the batrachians (amphibians), Huxley and Parker difier. 

 Gruber's studies of mammals agree in essentials with those of 

 Parker. Kolliker, in the second edition of his ' Entwicklungs- 

 geschichte,' delivered an imdecided judgment on this question; he 

 could not, however, confirm the results of Eeichert. 



New investigations are therefore imperatively demanded to settle 

 data which involve such important issues. 



Krukenberg's Studies in Comparative Physiology. — Want of 

 space prevents our doing more than suggest to our readers to study for 

 themselves Dr. C. F. W. Krukenberg's valuable essays on a number of 

 physiological topics, including : the mechanism of the chamseleon's 

 changes of colour,! the respiratory phenomena of various inverte- 

 brates, J the effects of curare and strychnine on the lower Medus£e,§ the 

 action of the heart in Salpa,\\ the pendulum-like movements of the foot 

 in Carinaria,'^ and the relation between the pigment of the liver and 

 the colouring matters of the blood among invertebrate animals (with a 

 plate of absorption-spectra).** There are also two interesting notices 

 on Ctenophora, to which we refer under Coelenterata, infra, pp. 52-55. 



* Croonian Lecture, 1858. 



t 'Vergleichend-physiologische Studien,' Part 3 (8vo. Heidelberg, 1880) pp. 

 23-65. X Ibid., pp. 66-123. § Ibid., pp. 124-46. 



II Ibid., pp. 151-76. •! Ibid., pp. 177-80. ** Ibid., pp. 181-91. 



c 2 



