410 Scientific Ilevien>9>. 



iiually exposed to the influence of successive portions of the sur- 

 rounding element. This union of the locomotive and respiratory 

 functions in the same apparatus we shall find still more strikingly 

 exemplified in the Ktenophorae. 



The Ktenophorae possess a much more complete circulating sys- 

 tem ; its extent and mode of distribution, however, have hitherto 

 been little more than matter of conjecture; and we are indebted to 

 the author himself for the first account of it in all its perfection. 

 He has traced the connection of the vessels with most success in the 

 genus Cestum ; but as the vascular system in the animals of that 

 genus, owing to their singular form, presents several peculiarities, 

 which would render the whole difiicult to be understood without 

 the help of figures, we prefer giving the aixthor's description of it 

 in the Beroe. This animal is of the usual oval form, the body be- 

 ing traversed by the cavity of the stomach and the short canal for 

 the transit of water, which opens posteriorly. " From the poste- 

 rior end of the body where the short tube opens, arise eight canals 

 of uniform diameter, which run forwards towards the large anterior 

 opening or mouth, near the margin of which they terminate in an 

 annular vessel. In this course they are placed immediately under 

 the rows of pectinated organs or fins, whose direction they follow 

 exactly, and send ofi^ large branches, which are distributed both to 

 to the adjacent parts of the surface and deep into the substance of 

 the body. On the parietes of the large cavity within the body two 

 large vessels are conspicuous, which rise, by a narrow commence- 

 ment, from the annular vessel and run backwards, taking up in 

 their course all the twigs which come from the first-mentioned ex- 

 ternal vessels. It is probable that the two internal vessels, which 

 are to be regarded as veins, terminate in another aniiular vessel at 

 the posterior extremity of the body, and that from this posterior 

 annular vessel, after it has received small twigs conveying nutri- 

 tious fluids from the stomach, the eight external caoals, which, in 

 their turn, are to be looked upon as arteries, take their rise. Such 

 a connection, however, though extremely probable, has not been 

 actually traced, on account of the difficulty of investigation, which 

 arises from the great thickness of the body at the posterior part." 

 P. 15, 16. The vessels are filled with a transparent and colourless 

 fluid, with small globules of a light yellow colour, which may be 

 seen in motion. The author adds : " From the distribution of the 

 vessels just described, it wiU appear evident that the rows of fins 

 perform a twofold function, being at the same time organs of loco- 

 motion and of respiration; and that they are consequently to be re- 

 garded as gills." lb. 



From these facts, also, it further appears, that in the Acalepha of 

 this order the water is renewed on the surface of the respiratory 

 organs by means of a mechanism more or less similar to that which 

 has been observed in a great variety of other invertebrate animals. 

 But this is a subject on which we cannot enlarge on the present 



