ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 203 



systems wliicli connect the bulbs with the more distant parts of the 

 brain, and, partly also, with one another. 



From the rich possession of nerves by Jacobson's organ in an 

 eight-week old embryo, and their disappearance in older embryos, we 

 may conclude that the organ is now in a rudimentary condition, as 

 compared with what it was in ancestral forms. 



Eggs of Birds.* — Prof. Tarkhanoff records a very interesting 

 inquiry into the structure of the eggs of birds. 



He finds that albumen of the eggs of the Insessores (ousel, 

 canary, pigeon, &c.) notably differs from that of the autophagous 

 birds (hens, ducks, geese, turkeys). When boiled it remains trans- 

 lucid ; it is fluorescent ; its rotation-power on the plane of polarization 

 is feebler ; when diluted with much water it does not give a white 

 deposit, but only gives a feeble opalescent coloration to the water ; 

 finally it has a stronger basic reaction than the white of the eggs of 

 the hen. It may, however, be transformed so as to become like it 

 by various means, namely, the addition of neutral salts, or of bases, 

 or of concentrated acetic and lactic acids, or even of carbonic acid. 

 The most remarkable fact, however, is that the same result is also 

 arrived at by incubation, and Prof. Tarkhanoff considers that the 

 modifying agency in this case is the yolk ; when moderately heated 

 with yolk in closed vessels, during twenty-four hours or more, it is 

 transformed into albumen like that of a hen's egg. As to the manner 

 in which the yolk acts on it, it still remains unsettled ; the suppo- 

 sition that the diffusion of salts is the cause of the change proved not 

 to be true; and the cause must be searched for perhaps in the 

 diffusion of gases. The interesting question, as to the albumen of 

 hens' eggs not also undergoing the same stages of development 

 within the ovarium, cannot yet be solved satisfactorily ; but during 

 his experiences M. Tarkhanoff observed once the most interesting fact 

 that a small ball of amber introduced into the upper part of the 

 ovarium occasioned the deposition of albumen around the ball, and 

 the formation of a shell, that is, the formation of a quite normal egg 

 with its chalazae, and other particulars of structure. This observa- 

 tion would thus strongly support the mechanical theory of the 

 formation of the parts of an egg around its yolk. 



Chemical Composition of the Egg and its Envelopes in the 

 Common Frog-t — P. Giacosa, to isolate the envelope, placed the eggs 

 for some hours in lime water, whereupon the envelope dissolved while 

 the yolk settled down to the bottom. The filtered solution, treated 

 with acetic acid of 10 per cent., yielded a flocculent precipitate, which, 

 after repeated washing with acetic acid and pure water, gave by 

 analysis 52-71 per cent. C, 7-1 H., 9-33 N., 1-32 S., and 0-42 ash, 

 whence the author infers the presence of a mucin. This substance 

 resists putrefaction, and does not reduce copper salts till after boiling 

 with dilute sulphuric acid. The author intends to study the products 

 of this decomposition, but as he has not been able to detect the 



* Mem. Soc. Nat. St. Petersburg, xiii. (1883). See Nature, xxix. (1884) p. 461. 

 t Journ. Ohem. Soc— Abstr., xlvi. (1884) pp. 198-9, from Gazetta, xiii. p. 171. 



p 2 



