INFUSORIAL ANIMALCULES. 29 



further, that the emission of light was restricted to some only of 

 these. Those indi^-icll^als which were not phosphorescent were quite 

 clear, whilst those which emitted light were filled with yellowish 

 brown matter, which he considered to be developed ovaries, so that 

 here also the development of light would appear connected with that 

 of the ova. 



In his paper on the Infusoria of the Chalk, (1840), that observer 

 also stated that one of the most remarkable facts elicited in the course 

 of his examination of the sea water, whilst in a state of phosjiho- 

 rescencc, was, the presence of several species of two genera, the 

 members of which have siliceous loricse, which are abimdant, not 

 only in the chalk marls of Caltanisetta, Sicily, Oran, Zante, and 

 Greece, but are those forms which, fi'om the incalculable number of 

 their very minute lorica?, compose the chief portion of the marls, 

 which depend for their origin on the remains of species of Infusoria ; 

 and fiu'ther, that they belong to genera, species of which had not 

 then been seen in the living state. 



Section XI. — Classiftcation of Infusoria. — Among the various 

 an-angements proposed for the distribution of animalcules by dif- 

 ferent natiu-alists — and we have not a few, as the minuteness of 

 these creatures, and the imperfections of oiu* microscopes, until 

 lately, allowed ample field for the imagination to run wild — two 

 appear to me to merit particular notice, and these, it is worthy of 

 remark, are the productions of men who have laboiu-ed for years in 

 making actual observations on them. The fii'st is by 0. F. Midler, 

 whose posthumous work, entitled Animalcula Infusoria Fluviatilia et 

 Marina, appeared in the year 1786. On tliis arrangement is founded 

 my Natural History of Animalcules, prepared in 1832; between 

 these two periods the additions to this branch of natural history, 

 fi'om actual observation, was not veiy gi-eat ; indeed, until the latter 

 work appeared, this subject could not be said to have assumed a 

 definite character, and was lui known to the English reader. 



The laborious and long-continued observations of Prof. Ehrenberg, 

 in Germany, have enabled him, after several revisions and amend- 

 ments, to present us with a classification, which, in my opinion, will 

 remain as long oiu" standard, on this subject, as that of Midler has 

 been. It is ciu-ious, however, to observe, that in all the publica- 



