10 On the present state ofZooloyy. 
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 potygastric 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.f 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 hy 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, u'ntil 
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- 
* Mikrographische Beitrage 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. 18S5, pp. 23-28 ; and pp. 73-76. 
\ See Ann. des Sci. Nat. 1835, torn. iv. p. 290. 
Zool. Trans, vol. i. p. 10. 
