10 On the present state of Zoology. 



but one type pervaded the whole animal kingdom, which, however 

 modified in different groups, was capable of being traced from man 

 downwards to the Rotatoria, and even to the polygastric monad. 

 Hardly less striking than in the case of the Infusoria, is the astonish- 

 ing accuracy with which the German naturalists have investigated 

 the structure of the more minute Entozoa. We may refer to M. 

 Nordmann's work* as evincing the patience with which these re- 

 searches have been conducted in the instance of certain parasitic worms 

 found in the eyes of some of the higher animals. The whole group 

 is one which stands much in need of further examination ; and we 

 are glad to find that it has recently engaged the attention of one of 

 our own countrymen, Mr Owen, who has suggested several hints for 

 a better arrangement of its heterogeneous contents.-]- Although not 

 in all cases offering any difficulty to the anatomist in respect of their 

 size, we have already alluded to the Acalepha as possessing an ex- 

 tremely delicate and transparent organization. M. Ehrenberg has 

 availed himself of this very circumstance for employing the same me- 

 thod of examination in this class, already so successfully resorted to 

 in that of the Infusoria.^ By means of indigo, used for colouring 

 the water in which these animals were preserved, he has detected the 

 existence of anal openings, which, previously to this experiment, 

 were thought wanting. The same observer has satisfied himself, that, 

 notwithstanding their supposed simple structure, they possess bran- 

 chiae, eyes, muscles, and nerves. It will be remembered that these 

 last had been previously discovered in the Acalepha by Dr Grant. § 

 The species principally examined by Ehrenberg was the Medusa au- 

 rita. In the same paper containing the result of his researches, are 

 detailed some observations on the structure of the Echinodermata. — 

 Allusion has been also made to the Polypi, as a group which, until 

 lately, had been much misunderstood, owing to our slight acquaint- 

 ance with their internal organization. Milne-Edwards, to whom we 

 are mainly indebted for removing part of the obscurity which hung 

 over these animals, has made them the subject of two new memoirs 

 read to the Royal Academy of Sciences at Paris during the past year. 

 We must refer to the memoirs themselves for some interesting par- 



* Mikrographiscke Beitr'age zur Naturgeschichte der wirbellosen Thiere. 

 Berlin, 1832. 4to. Some extracts from this work will be found in the Ann. 

 des Sci. Nat. for 1833, torn. xxx. pp. 268 and 373. 



f See Proceed, of Zool. Soc. 1835, pp. 23-28 ; and pp. 73-76. 



\ See Ann. des Sci. Nat. 1835, torn. iv. p. 290. 



§ Zool. Trans, vol. i. p. 10. 



