INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 583 



algae. On removing these it is seen clinging like a flake of jelly, 

 shining like crystal. The season of their occurrence is limited to 

 June and July. They were not found in September and October, any 

 more than in the spring. 



Every zoologist who has attempted to keep these creatures in 

 captivity has been reduced to despair by seeing them perish in a little 

 time, whatever may have been done to render the aquarium comfort- 

 able for them. But this marsh species, forced no doubt by vital com- 

 petition to accommodate itself very gradually to great vicissitudes, has 

 become hardened by this process ; and the proof of this is that it may 

 be very well preserved for weeks together in the smallest bottles, with 

 a few hundred grammes of the water of the canal and a few green 

 algfB to keep up a small supply of oxygen. Under these circumstances, 

 si:>ecimens have been transported with the greatest facility from Cette 

 to Lausanne, and kept there for months without the least trouble. 

 This species, being so accommodating, will be very welcome to those 

 who desire to observe these animals for a long time in captivity. 

 Cladonema radiatum Duj., and other microscopic Medusce, also bear 

 captivity, but these are scarcely visible to the naked eye, whilst this, 

 being of the size of a half-franc (Swiss money), is much more suitable 

 for all sorts of manipulation. 



Moreover (and this is the most interesting point), it presents one 

 of the clearest examples of the influence of the circumambient medium 

 upon the gradual modification, and finally, transformation of one 

 species into another ; for certainly our Medusa has originated from 

 an importation of the large Cosmetira punctata, the form of which it 

 reproduces on a small scale, repeating its whole organization en 

 diminuiif. Thus reduce the larger animal to the dwarf size of a half- 

 franc piece, coloui' the canals and the stomach green, change the rose- 

 colour into violet, blacken the tentacles, and you have by these 

 modifications transformed the Cosmetira of the sea into that of the salt 

 marshes.* 



Charyhdea marsupialis.t — This Medusa, which lives at the 

 bottom of the sea, and exhibits a large amount of asymmetry, is in- 

 teresting especially on account of the different reports given of it by 

 Gegenbaur and Fritz Miiller. Difficult to obtain, its structure and its 

 systematic position have long remained uncertain : it was distinguished 

 by F. Miiller from the genus Tamoya, on account of the following 

 characters ; tlie edge of the bell (velum) was divided into lobes, 

 the stomach was provided with accessory canals, the " grappling lines" 

 opened into the lateral canals and not into the lateral pouches, the 

 stomach and oral infundibulum were confluent, and the gastric fila- 

 ments hollow and not solid. 



Professor Glaus now states, that in the first three points Charyhdea 

 does resemble Tamoya, that point four is of no value, and that as to 

 the hollow filaments connected with the stomach there are no such 

 in any Medusa; they are, in fact, always solid. The ectodermal 

 investment is reported as having just the same characters as in other 

 * ' Anu. and Mag. Nat. Hist.,' iii. (1879) p. 385. 

 t ' Arbeit. Zool. Inst. Univ. Wien,' ii. (1878) art. 2. 



