568 



SUMMARY OF CUKRENT RESEARCHES RELATING TO 



in breeding. He defines the difference in degree between hair and wool, as 

 expressed in the method of attachment of the epidermal scales which form 

 the external covering of the fibres. The modifications which are noted 

 concern all the various parts of which the hair is composed. In the fleece 

 of the semi-wild sheep of Central Asia, three different classes of fibres may- 

 be distinguished often in the same lock of wool ; (a) those which have all 

 the characteristics of true hair in their most marked degree; (6) those 

 which resemble alpaca and mohair fibres ; (c) those which are true wool. 

 " All the variations observed are formed in the fibres from the same sheep 

 in the various races which inhabit Central Asia, while in most of the sheep 

 inhabiting other parts of the world the usual variations from the normal 

 types are less distinctive in their character and confined within narrower 

 limits. This seems to point to the mountainous regions of Central Asia as 

 the district from which the present domestic sheep has spread. 



B. INVERTEBRATA. 



Vitality of Encapsuled Organisms.* — Herr M. Nussbaum noticed a 

 living embryo in a Daphnia which had been expelled from the gastric 

 cavity of Hydra; of this Daphnia, as of another that was swallowed, 

 nothing remained of the soft parts. This observation showed that the 

 embryos of the Cladocera that were seized were not killed by the poison of 

 the stinging organs, and that the egg-shell protected them from the 

 " digestive ferment of the Polyps." An experiment with absolute alcohol 

 used to poison a pregnant female Daphnia showed that while the adult 

 was killed the young remained capable of further development when trans- 

 ferred to pure water. Considering the enormous voracity of Hydree this 

 immunity of the Daphnia embryos is important, not only for the latter but 

 also for the polyps. The resistance of the embryos being due to the 

 presence of a hard egg-shell, the whole phenomenon is comparable to the 

 power possessed by many lower organisms of forming a temporary capsule 

 to protect themselves against desiccation ; and in the plant-world there are 

 other analogies — fruits serve as food for animals, but their seeds pass 

 uninjured through the digestive tract. 



Influence of Medium.t — M. A. de Varigny has made a number of 

 experiments as to the effect of alterations of medium on Beroe ovata, Aurelia 

 aurita, and Pagurids. Some of these may be thus summarized : — 



Beroe . . Fresh water Contraction and death. 



„ . . Equal parts fresh and salt Contraction, with recovery 



after replacement in salt 

 water after 15 mins. 



„ . . 1 part fresh to .3 salt Same effect. 



„ .. „ „ 5 salt No effect. 



„ .. Sea-water at 31° More rapid movement of 



ciliated plates. 

 Aurelia .. „ „ Rhythmic movements re- 



placed by rapid and 

 spasmodic, but normal 

 again in 11 mins. 



Beroe . . „ at 35° Spasms ; normal again in 



25 mins. 



„ .. „ at 40° Death. 



„ . . „ +2 per cent, sulphate of copper . . Rapid death. 



„ , . „ +1 „ bichromate of potassium Reduction of ciliation and 



contraction and slow 

 death. 

 „ .. „ + 1-5 per cent, chloral hydrate.. .. Slow death. 



* Zool. Anzeig., x. (1887) pp. 173-4. 



t Soc. de Biol., 1887. Cf. Biol. Centralbl., vii. (1887) pp. 127-8. 



