60 M. Ehrenberg's Researches on the Infusoria. 



proach to each other, their limits are confounded, and the 

 outer covering of the body becomes folded. Viewing all these 

 phenomena, he does not fear to state that the small vibratory 

 moving bodies which are placed in two longitudinal series in the 

 internal cavity of the body, are to be regarded as internal 

 branchice, and he means to maintain this opinion till more de- 

 tailed observations shall assign lo them some other function in 

 their economy. The multiple hearts, which are found, accord- 

 ing to Prevost, in the Chirocephales, still demand particular at- 

 tention. They are not placed in two series, but simply one be- 

 hind the other ; and they may rather be compared to the dorsal 

 vessel of insects than to the organ now under review. Besides, 

 the whole form of these Entomostracea resembles more one of 

 the larvae of those insects which copulate previous to the time 

 of their development, as happens in the Orthopteres and the 

 Hemipteres. 



V. On the Nervous Si/stem of the Infusoria. 



Professor Ehrenberg is apprehensive lest he should be charged 

 with temerity for admitting the existence of an isolated nervous 

 system, forming an apparatus similar to that existing in vertebral 

 animals and in insects, in a class of animals which have been sup- 

 posed to be without any structure at all, according to many an- 

 cient observations, and many recent theories. Up to this period, 

 his remarks on the nervous system of the Infu sores have only 

 been general, and he has treated particularly only of the Hyda- 

 tina senta ; here, however, he favours us with some details to 

 prove that this system must be recognised as existing in the mi- 

 nute beings which are now occupying our attention. 



In most animals in which a nervous system is generally ad- 

 mitted, the nerves are usually distinguished by their whitish 

 colour; the muscular fibres, and the vessels are of a colour 

 somewhat red or yellowish ; the tendinous fibres are bluish, and 

 the cellular tissue is transparent and clear like water. But these 

 characters are not sufficient when we are called to distinguish, 

 with certainty, nervous filaments which are exceedingly delicate; 

 and doubts exist even when the filaments are of a considerable 

 size. Another character, which is often very decisive, consists 

 in certain bluish zigzags which present themselves during the 



