802 KEOOKD OF CURRENT RESEARCHES RELATING TO 



It is none tlie less evident that the normal hosts of the Gordii are 

 all animals exclusively or temporarily aquatic. Water is, in fact, the 

 normal medium of the Gordii. It is in the water that they become 

 adult, and that they reproduce ; it is in the water that their larvae 

 live at first on their escape from the egg ; and it is also in the water 

 that their migration must be effected. 



The parasitism of the larvae of the Gordii in terrestrial animals 

 has an essentially abnormal and exceptional character ; and in order 

 to explain it we must have recourse to very peculiar conditions. In 

 plains these are realized by the periodical inundations and systematic 

 irrigations, — in mountainous and hilly countries the escaping torrents 

 carry away everything in their course, the insects perish, and the 

 worms which they contain are set at liberty. 



The frequency of the larvae of Gordii in insects, which is cited as 

 an objection to the author's views, is more apparent than real. It 

 must be remembered that the insects are represented by a great 

 number of species, and are sought after by most naturalists. 



Excretory System of the Trematoda and Cestoda.* — M. Frai- 

 pont, in a preliminary notice as to the results at which he has arrived, 

 says that 



(1) The excretory apparatus arise from small, and not numerous, 

 infundibula, which communicate with the spaces between the organs 

 by an orifice placed in their lateral wall. The greater part of every 

 infundibulum is formed by a single cell armed with a vibratile 

 flagellum. 



(2) In the intervening spaces he finds a system of very delicate 

 canalicula, which are arranged in a radial fashion. 



(3) The infundibula are arranged almost symmetrically on either 

 side of the middle line, and each gives rise to a small canal, several of 

 which converge, anastomose, and then open into a system of large 

 vessels, placed at six definite points in the body, and symmetrically 

 disposed two by two. There may, consequently, be said to be three 

 pairs of segmental organs, and it is of interest to remember that in 

 the larval IJirudinea there are three pairs of segmental organs in the 

 posterior region. 



(4) The system of large canals form two lateral trunks, which 

 rapidly bifurcate ; of the branches thus formed, one passes towards the 

 middle line to anastomose with its fellow of the opposite side. The 

 other passes along the whole of the lateral edge of tlie body, and 

 after giving oif diverticula which increase in complexity with the 

 age of the individual, terminate blindly. The trunks themselves 

 open into a terminal reservoir, which is filled with highly refractive 

 corpuscles, and opens to the exterior in the middle line and at the 

 hinder end of the body. 



The preceding being an account of what is found in such Trema- 

 toda as Polystomum integerrimum, Octohotlirium lanceolatiim, and Diplo- 

 zoon paradoxum, we have next to inquire what obtains in the Cestoda. 

 " In Caryopkyllceus mutabilis there is the following arrangement : — 



* ' Bull. Acad. Roy. Belgique,' xlix. (1880) p. 397. 



