4D& Stientifie Remetpg^ 



tive cavity. Organs of locomotion, small filaments disposed in rows 

 on the external surftice of the body. 



2. Discophorae, (Scheibenquallen.) With a large central diges-: 

 live cavity. The organ of locomotion of a discoid or bell-shaped" 

 figure, forming the principal part of the body. 



3. Syphonophorge, (Rohrenquallen.) Digestive apparatus con- 

 sisting merely of absorbent tubes, without a central cavity. Or- 

 gans of locomotion one or more contractile cavities opening exte- 

 riorly^ or air bladders ; often both together. 



"We shall not attempt to follow the author into the subdivisions of 

 these orders, but, for the present, shall confine our notice to the in- 

 troductory part of the work, which, being devoted to general con- 

 siderations respecting this tribe of animals, and containing a very 

 clear and instructive account of their anatomy and physiology, pre-, 

 sents topics of more general interest. To one or two of these we 

 would now venture to call the attention of our readers. 



One rather important fact relative to the structure of the Kteno- 

 phorae, is, in a great measure, a discovery of the author himself. 

 We shall give it nearly in his own words. " From the bottom of 

 the stomach a short and straight canal leads towards the posterior 

 extremity of the body, and there opens externally. This structure 

 has much resemblance to an intestinal canal, yet it seems to be 

 connected merely with the peculiar mode of locomotion in these 

 animals, and, properly speaking, forms no part of the digestive 

 organs. In swimming, the mouth of the animal is kept wide open, 

 and is directed forwards, hence the water enters the cavity of the 

 stomach, out of which it must be afl^orded a free exit at the op- 

 posite extremity, otherwise it would oppose such resistance as would 

 eflTectually prevent all progressive motion." p. 12. Fabricius, 

 (Fauna Groenlandica, p. 361. seqq.,) seems to us to have observed 

 this structure in some species of Beroe; at the same time he cer«. 

 tainly was not aware of the use which is ascribed to it by the 

 author. 



The organs of locomotion are either active or passive. In the 

 Ktenophorae they are very remarkable, differing altogether from 

 those of the other two tribes. The author thus describes them : 

 " They consist of very small pectinated organs, which are disposed 

 in long narrow stripes on the external surface of the body, being 

 placed with their flat surfaces contiguous to each other. Each pec- 

 tinated organ is made up of a considerable number of short, flat, 

 pointed filaments, of equal length, set together like the teeth of a 

 comb, which, in the Ktenophorae of the usual oval form, have their 

 points directed backwards towards the closed extremity of the ani- 

 mal. They are moved in the same way as fins, being slowly erect- 

 ed and then struck backwards with a sudden motion. When all the 

 rows of these pectinated fins are set in motion, the animal is mov- 

 ed more or less rapidly onwards with the wide opening or mouth 

 directed forwards. In most cases the rows of . fins are uncovered : 



