54 RAMBLES OF A NATURALIST. 



the philosophical doubts of the majority of inquirers, 

 nothing authorised the admission in any general 

 manner, that these animals were characterised by a 

 well-defined nervous apparatus ; nevertheless M. 

 Blanchard has shown that such is the case, and he 

 has confirmed or rectified by numerous examples the 

 facts which had been obtained in reference to the 

 Distomata and the Nematoides* by Bojanusf, MehlisJ, 

 Laurer , Cloquet ||, &c. He has shown that the 

 Taenias IF present a most singular arrangement, which 



* The Distomata are a group of intestinal worms comprising the 

 Liver-fluke, which is so common in sheep, together with all the 

 worms which are allied to that form. The group of the Nemato'ides 

 is composed of the Ascarides, and all the genera which are allied to 

 that type. 



f Bojanus, who is. one of the most distinguished anatomists of 

 Germany, commenced in 1817 a series of anatomical observations on 

 intestinal worms, which had before that time been studied only in 

 reference to their external characters. He was the first to discover 

 the Sporocysts, and to recognise the nature of the Cercarese. We 

 moreover owe to him several important works, amongst others a 

 magnificent anatomical memoir on the European Tortoise. 



J Mehlis was one of the first who noticed the nervous system 

 of the Trematoda, in an anatomical description of the Distoma 

 hepaticum and D. lanceolatum. 



We owe to Laurer, amongst other works, some highly interest- 

 ing researches on the anatomy of the Amphistoma. 



|| M. Cloquet has published, on the anatomy of the Ascaris 

 lumbricoides, a memoir which has long been the best on the subject. 



^[ The Tsenia, which is vulgarly regarded as a solitary worm, 

 does not by any means merit this appellation, for even in man 

 several of these animals are often simultaneously present, and 

 certain species occur in large numbers, more especially in fishes, 

 many individuals being present in the same intestinal tube. We 

 would here remark that in accordance with Van Beneden's view 

 each Tsenia is not an individual, but an aggregation of many indi- 

 viduals, which being at first united, become successively isolated, 



