186 Bibliographical Notices. 



interesting group for the communication of any new or rare British 

 species. We are also rejoiced to hear that he contemplates pre- 

 paring a ' Phycologia Gerraanica,' a work which cannot fail to prove 

 most instructive. 



The points of interest which are presented by the minute objects, 

 of which so many species arc here illustrated, are surpassed perhaps 

 in scarcely anv order of created beings, and the results which have 

 arisen from their study, which is but yet in its infancy, are as im- 

 portant as unexpected. Not only is the question of their nature and 

 affinity a very interesting one, and the variety and beauty of form 

 most striking, but the study of these organized atoms bids fair to 

 afford the geologist quite a new resource in his investigation of the 

 comparative age or identity of strata. They exist in all climates, and 

 in situations where neither other animals nor vegetables (to which- 

 ever class we assign these beings) can exist. Above 120 species 

 were discovered by Dr. Hooker in very high latitudes, and by sound- 

 ings far beyond the limits of ordinary vegetable or animal forms, and 

 many of these when sent to Dr. Ehrenberg after a long voyage were 

 all but alive. Whole strata are formed of their siliceous skeletons, 

 and it seems that sometimes they are propagated to a certain extent 

 in subterranean strata at the present day. 



Authors have been much divided as to their nature, and while Dr. 

 Ehrenberg doubts not they are animals, and believes that he has dis- 

 covered within them a digestive aj^paratus and other organs such as 

 exist in acknowledged infusoria, otliers, amongst the number of whom 

 we must confess oui'selves to be, as decidedly incline to consider 

 them Algae, and as constituting a most important link in the series. 

 This question, like others relating to the group generally, is well dis- 

 cussed by Kiitzing, and we think it may be acceptable to our readers 

 to offer them a translation of his remarks. 



The following arguments are brought forward by Ehrenberg in 

 favour of their being animals : — 



1. They have, in part, a peculiar spontaneous motion which is 

 effected by particular organs. 



2. Many have a lateral opening, ro«nd which are seated globular 

 bodies, which, like the caeca of Infusoria, become blue in an infusion 

 of indigo in water, and must therefore be regarded as stomachs. 



3. The shells of many Diatomece remind us by their structure and 

 form of that of Gastropods and similar Alollusca. 



As regards the first it may be remarked, that spontaneous motion 

 also takes place in lower vegetable forms, which likewise is effected 

 by peculiar ciliary organs. Witness the observations of Unger on 

 the spores of Vancheria vluvuta, and those of Flotow on Hcematococciis 

 pluvialis*. And I may here mention my own in the ' Phycologia 

 Generalis ' on Ulothrix zonata and other Algse, which show that in 

 all these lower forms appearances of motion are exhibited, which can- 

 not be distinguished from those which take place in the Infusoria. 



* To these may be added various observations of Tluu'ot and Decaisne, 

 not only in the lower Algae, but in the acrosperms of Fuci. 



