546 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the ovum and the escai:)e of the embryo, the male Alytes retiring 

 with the eggs wound round its legs to holes in the ground away 

 from light and warmth. On warm nights in July (with the thermo- 

 meter at 20° C.) the male Alytes carries his charges down to the 

 water, and they then effect their escape, as above described. If the 

 atmospheric conditions are unfavourable the Alytes, guided by " son 

 instinct barometrique," defers its passage from the land to the water. 



Development of the Nervous System of Forella.*— An account 

 is given by V. Kohon of his observations on the development of 

 the cerebro-spinal system in the trout. Briefly summed up, his 

 results are that the first nerve-cells, distinctly recognizable as such, 

 occur in this fish in the dorsal (sensory) tracts of the cerebro-spinal 

 system. These " cells of Reissner " are multipolar, lie on either side 

 in a longitudinal series (6 to 8 pairs in a myomere at the time of 

 escape of the embryo from the ovum), and occur in the spinal cord 

 earlier than in the brain. In the spinal cord they have relations to 

 the dorsal roots of the nerves of the same, and of the opposite side. 

 These cells occur in much the same fashion in the adult trout. 



Incubation of Eggs in Confined Air— Influence of Ventilation 

 on Embryonic Development.! — C. Dareste describes the results of 

 his experiments on the development of the embryos of fowls in a con- 

 fined atmosphere. 



The eggs were placed in a 12-litre incubator, all the apertures of 

 which were kept closed for 21 days. When opened several eggs 

 were found hatched, but the greater number had perished, owing to 

 the development in the albumen of microscopic organisms. The 

 organism most often met with was a plant similar to yeast. 



In a second series of experiments the air was saturated with 

 moisture, and in this case the albumen liquefied and leaked through 

 the shell where it solidified in layers. This liquefaction appeared to 

 be an obstacle to hatching ; nevertheless, the embryos from the sound 

 eggs had here also reached their full period, whilst those from the 

 infected eggs had perished, stifled by a species of Aspergillus that 

 developed a mycelium in the interior of the albumen, then formed 

 green fructifications in the air-chamber, and finally on the walls of 

 the shell. 



The author concludes that air, modified by embryonic respira- 

 tion, exercises no direct influence on the development and life of the 

 embryo ; but only an indirect one by facilitating the excessive deve- 

 lopment of the parasitic organisms. Hence the necessity of renewing 

 the air of incubators. In the struggle for life between the embryo 

 and the parasites the advantage is in favour of the former, if the air 

 be renewed and is sufficiently dry; whilst in air that is stale or 

 saturated with moisture the advantage is in favour of the parasitic 

 organisms. 



* SB. K. Akad. Wiss. Wien, 1884, pp. 39-56 (2 pis.), 

 t Comptes Rendus, xcviii. (1884) pp. 924-6. 



