352 ANIMAL PAEASITES. 



anus, and both these pass outwards together, whilst the structures 

 regarded by Luschka as valves may unite to form the tube, beset 

 with spines, which serves as the copulatory organ. 



In this way the probable developmental history of the worm 

 presents sufficient data for the placing together the two worms, 

 although hitherto experimental evidence cannot be furnished either 

 for the production of Trichina from eggs of Trichocephalus dispar, 

 or for the conversion of Trichina into Trichocephalus dispar. 



For these reasons, however, I regard the Trichina as the brood 

 of Trichocephali engaged in migration, by swallowing which we 

 infect ourselves with the Trichocephalus dispar of both sexes. At 

 the same time, however, I may also observe, that if experiment 

 should in any way prove that the Trichinae are only converted 

 into male Trichocephali, I would immediately accept this view, 

 improbable as it is a priori. At any rate, I only hope for a 

 decision of this question by experiment, although, determined by 

 zoological reasons, I already regard the relationship of the 

 Trichina and Trichocephali as certain. But the migrations of 

 the Trichina are also of great importance for the theory of the 

 nematode-like animals described by authors as Hamalozoa, which 

 have always hitherto appeared to be asexual worms. As far as 

 they have been referred to in the human subject, we might 

 perhaps think that, if worms at all, they must have been in most 

 cases the youngest, migrating brood of Trichocephalus, before it 

 had yet fastened itself, and become encysted and converted into 

 Trichina. That the brood of the Nematoda, like that of the 

 Ceslodea, may get into the blood during its migration has already 

 been stated. 



By the opinion just announced, as to the production of the 

 Trichina, I have come into opposition with that of Herbst 

 expressed in the 'Nachrichten von der G. A. Universitat, &c, 

 zu Gottingen/ No. 19 for 1851, and No. 12 for 1852, and which 

 has recently found much acceptance. 



Herbst distinguishes the following species of Trichina : 



1. The Trichina of the hawk, the owls, the crows, and the 

 woodpecker, regarded by him, notwithstanding their different 

 sizes, as identical, and which are derived from Filaria attenuata, 

 just as the species occurring in other birds will be derived from 

 such Filaria as are peculiar to these birds. 



2. Those occurring in man, which, at the same time, are very 



