92 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



to these are added certain special facts which the Cristatella present, as, 

 for example, having a foot which is everywhere contractile, and their 

 secreting, like the Gasteropoda, a copious viscid matter ; we shall be led 

 not only to associate them with the class of the Mollusca, but likewise 

 to introduce along with them all the animals which are farther down in 

 the scale. Before, however, maintaining this as an irrefragably esta- 

 blished fact, we shall request another opportunity of explaining some 

 additional results. 



[From Annals of Natural History, April 1842.] 



Mr. Ralfs on four new Species of Desmidium. Mr. Ralfs observes 

 that this natural genus is not well defined, either in Agardh's Conspec- 

 tus criticus Diatomacearum, or in any of our British works. Its best 

 distinctive characters seem to consist in the crenated appearance of its 

 filaments, which is least evident in D. mucosum. These filaments, 

 which are generally twisted in a regular manner, are of a pale green 

 colour, simple, fragile, short and straight. The species are found during 

 a great part of the year, in clear shallow pools, or in old peat bogs ; the 

 filaments being scattered in loose bundles in the water, or forming a 

 thin gelatinous fleece at the bottom of the pool. The species ascer- 

 tained by Mr. Ralfs are named by him D. cylindricum, mucosum, Swart- 

 zii, and Borreri. (Report of Botanical Society of Edinburgh.} 



[However indefinitely characterised may be this Genus in Agardh 

 and our British works, we think it perfectly satisfactorily determined in 

 the great work of Ehrenberg, in which it will also be seen that Desmi- 

 dium Swartzii was determined forty years ago, and that D. cylindricum, 

 first observed by Greville in 1827, more properly belongs to the genus 

 Arthrodesmus.] 



Mr. Yarrell on Mucor observed by Col. Montagu growing in the Air 

 Cells of a Bird. In addition to the instances quoted in the 8th volume 

 of the Annals, page 229, of the growth of cryptogamous plants in the 

 bronchial tube of a Flamingo, and on the internal surface of the air cells 

 of an Eider duck, Mr. Yarrell refers to another example mentioned by 

 Col. Montagu, who says, " The cause of death appeared to be in the 

 lungs and in the membrane that separates them from the other viscera ; 

 this last was much thickened, and all the cavity within was covered with 

 mucor or blue mould. It is a most curious circumstance to find this 

 vegetable production growing within a living animal, and shows that 

 where air is pervious, mould will be found to obtain, if it meets with 

 sufficient moisture and a place congenial to vegetation. Now the fact 

 is that the part on which this vegetable was growing was decayed, and 

 had no longer in itself a living principle ; the dead part, therefore, became 

 the proper pabulum of the invisible seeds of the mucor transmitted by 

 the air in respiration. It w r ould indeed be impossible for such to vege- 

 tate in a living body, being incompatible with vitality, and we may be 

 assured that decay must take place before the minute vegetable can 

 make a lodgement to aid in the great change of decomposition." 



