180 RAMBLES OF A NATURALIST. 



isolated and joined together in floating colonies.* Here, 

 too, we beheld enormous swarms of those large spheri- 

 cal Beroesf, whose singular organisation has been 

 made known by M. Edwards, countless Medusas J, 



* These strange facts in reference to the reproduction of the 

 Salpae were discovered by Chamisso, the -witty author of Peter 

 Schlemil. He was the first who discovered that these Molluscs 

 live alternately isolated and in chains, and that these two modes of 

 existence recur in regular succession, and moreover, that the 

 aggregated individuals are always oviparous, whilst the isolated 

 individuals are always viviparous. These facts, which were 

 published in 1819, were for a long time discredited; but phenomena 

 of a similar nature which had not been previously observed have 

 been discovered in other groups of animals, and the researches of 

 Krohn have thoroughly demonstrated the accuracy of Chamisso's 

 observations. This subject is further noticed in Chapter IV., on 

 the Gulf of Castellamare. Krohn's memoir may be referred to in 

 the Annales des Sciences Naturelles. 



f The family of the Beroidse belongs to the class of the Acalephse. 

 (See the researches of M. Edwards in the Annales des Sciences 

 Naturelles.') 



J The Medusae constitute another family in the class of the 

 Acalephse. This group has been made the subject of a great 

 number of speculations, and has led to numerous researches which 

 have thrown much light on several very important questions. 

 Beaumur, trusting too much to first impressions, considered that 

 the greater number of the Medusae were simple masses of living 

 jelly. M. Dumeril, a member of the Institute, and the early friend 

 of Cuvier, injected the cavity of these animals with milk, when he 

 saw the fluid diffuse itself into a multitude of canals, which were 

 all arranged with the greatest regularity. This fact we believe first 

 revealed the existence of a true organisation in these singular 

 animals. Long after the observations of M. Dumeril, Ehrenberg 

 published a memoir on the Aurelia (Medusa Aurita), in which he 

 showed that this species possesses a remarkably complicated organi- 

 sation. The researches of Will, Agassiz, Huxley, and others, 

 although differing in reference to some points from the results 

 which had been obtained by the learned Berlin observer, have fully 



