EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 155 



taneously into a number of transverse segments, all of which become 

 new animals. The latter (not resembling the larvae) are free, swim in 

 every sense of the word, and have a disc-like body, the periphery of 

 which is divided into eight bifurcated rays at their extremities ; they 

 have a quadrangular mouth, in the form of a pendent tube, &c. As 

 they increase in size, the rays become shorter and shorter ; in the mean 

 time the intervals between the rays increase in extent, and give rise to 

 marginal tentacles ; to be brief, these animals become perfectly identi- 

 cal with their original parent (the Medusa or Cyanea). It is not then 

 the larva or the individual developed in the egg, which becomes changed 

 into the perfect Acalepha ; but the small ones formed by the transverse 

 and spontaneous division. This metamorphosis cannot be better com- 

 pared than to the development of the Salpa, although offering many 

 points of difference. The numerous observations of the author, made 

 during last autumn, convinced him that Chamisso has given every 

 necessary insight into their development. The Salpas resemble the 

 Acalephee, in the particular, that it is not the larva, but the young of the 

 larva which become perfect animals : it is not the individual, but the 

 race is changed. The author, in conclusion, refers particularly to the 

 observations of Graham Dalyell (Edin. Philos. Journ., Vol. XXI, 1836) 

 as confirmatory in part of several of his observations. December, p. 343. 



Quatrefages on the Anatomy and Physiology of Synapta Duverneea. 

 The genus Synapta was established by Eschscholts for those Holothu- 

 ridae with very delicate integuments, deprived of respiratory organs, and 

 possessing the property of adhering to foreign bodies in a similar man- 

 ner to the heads of Bardanus. It has been adopted by Jaeger and all 

 succeeding naturalists. All the species of this genus hitherto known, 

 have been discovered in the Red Sea, or in the seas of Asia and Ame- 

 rica. The presence then of these animals in our seas (the Islands of 

 Chausey, and on the coasts of La Manche) is alone an interesting fact 

 in Zoological Geography. 



The portion of this memoir which, had it not been so lengthy, it was 

 our intention to insert related particularly to the minute Anatomy and 

 Physiology of this interesting animal; to proceed with order in the 

 study of the several parts of the body of this Synapta, named by M. 

 Quatrefages S. Duvern&a, we had intended examining them successively 

 in the same order they are given in the original paper, viz. : 1st, the 

 integuments, 2nd, the trunk, 3rd, the digestive apparatus, 4th, the 

 organs of circulation, 5th, those of respiration, 6th and lastly, those 

 of generation. We must, however, refer our readers to the original 

 paper for the many interesting facts brought to light by the employment 

 of the microscope when examining the several tissues of this animal, es- 

 pecially as we cannot conveniently give at present the numerous illus- 

 trations accompanying the memoir. January, 1842, p. 19. 



Remak on the Production of the Blood-globules. In the blood of 

 chicks during the third week of artificial incubation, I found blood- 

 corpuscles, some of which were round, some pear-shaped and stalked, 



