226 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



mentary individuals, their object appearing to be that of at- 

 tract ins: and retaining the animalcules which serve as food to 

 the Bryozoa. All the individuals of any one colony are not 

 active, some of them, indeed, seeming as if dead, and actual- 

 ly having been so considered. This, however, is an error, 

 these individuals, although having lost most of their organs, 

 yet preserving the branches of the colonial nervous system, 

 and continuing to live at the expense of the juices elaborated 

 by the active members of the society. M. Claparede has 

 shown the mode of retrogressive metamorphosis of these ani- 

 mals, which retrace their steps over the same route of devel- 

 opment which they had traversed in their first growth. 



In a second paper upon parasitic crustaceans of the anne- 

 lids M. Claparede shows that of eleven species hitherto known, 

 all belong to the order of copepods, although constituting 

 eight or nine genera, divided into very different families. 

 Among these copepods some are free, and others are para- 

 sitic ; in others the female sex is completely parasitic, the 

 males being free ; while, again, the male, very much reduced 

 in volume, lives as a parasite upon its female, which itself is 

 a parasite of some other animal. 



M. Claparede, in the critical study of the annelids collected 

 by the British deep-sea expeditions some of them taken at 

 a depth of 650 fathoms has shown that these animals are 

 very largely the same, generically, with the kinds found near- 

 er the surface of the sea, and even along the shores. Con- 

 trary to the opinion of M. Quatrefages, he has ascertained 

 that lumbricoid worms are very common at great depths, and 

 that this group consequently contains species indubitably 

 marine. 3Iem. Soc. Phys. Genbve, XXII., 1870, 556. 



INFLUENCE OF SALT AND FRESH WATER ON CRUSTACEA, ETC. 



Professor Plateau has published some investigations as to 

 the effect of placing fresh-water articulates in salt water, and 

 salt-water articulates in fresh, the observations having been 

 directed more particularly to the crustaceans. Among the 

 conclusions arrived at are, that sea water has but a slight in- 

 fluence upon the aquatic coleoptcra and hemiptera in the 

 perfect state, but that it produces injurious effects upon 

 fresh-water articulates with a delicate skin, or furnished with 

 branchiae. Among crustaceans some species of Gammarus 



