104 LECTURE ■v^. 



out a semi-pellucid secretion. They are as simple as the so-called 

 salivary caeca in the Holothuria ; and their coexistence with a struc- 

 ture of the mouth, better adapted for trituration than any that 

 seems hitherto to have been detected in the Entozoa, is conformable 

 with the laws which regulate the coexistence of the salivary ap- 

 paratus in higher animals. Cloquet supposes that the thickened 

 glandular parietes of the oesophagus in the Ascaris lumhricoides may 

 provide a secretion analogous to that of salivary organs. Diesing* 

 has described four caecal tubes analogous to those in Gnathostoma in 

 species of his genus Cheir acanthus, in which he considers them, 

 erroneously according to Siebold, to be analogous to the ambulacral 

 vesicles in the Echinoderms. Mehlisf has also figured, in the 

 Strongyhis hypostomus, two white organs with blind extremities, 

 which are extended into the abdominal cavity on each side the 

 intestine, and which appeared to him to terminate in the animal's 

 mouth. These glands Mehlis supposed to pour out an irritating 

 liquor, which excited an increase of the secretion of the mucous 

 membrane, to which the parasite was attached. Dr. BaggeJ, has 

 more recently described a pair of blind secerning tubes in the 

 Strongyhis auricularis and in theAscaris acuminata, which unite 

 and terminate by a common transverse fissure on the exterior of the 

 animal, at a short distance behind the mouth, and to which he assigns 

 the same irritating office as that attributed by Mehlis to the glands 

 in the Strongylus hypostomus. 



The alimentary tube in a species of Ascaris infesting the stomach 

 of the Dugong is complicated by a single elongated caecum, arising at 

 a distance of half an inch from the mouth, and continued upward, so 

 that its blind extremity is close to the mouth. From the position 

 where the secretion of this caecum enters the alimentary canal, it may 

 be regarded as a primitive rudiment of the liver. 



The generative organs of the Coelelmintha are more simple than in 

 the androgynous Sterelmintha, or even than in the dioecious Echino- 

 rhynchi ; yet they are adapted for the production of a surprising 

 number of fertile ova. In the Linguatula the organs of both sexes, and 

 especially of the female, are more complex than in the Nematoidea : 

 I shall, however, briefly notice them before proceeding to demonstrate 

 the parts of generation in the human coelelminthic parasites. 



The male Linguatula, as in other dioecious Entozoa, is much 

 smaller than the female : the generative apparatus consists of two 

 winding seminal tubes or testes, and a single vas deferens, which 

 carries the semen from the testes by a very narrow tube, and after- 

 wards grows wider. It communicates anteriorly with two capillary 



* LXXXIX. -f XC. p. 81. taf. 2. fig. 6. % LXXXV. 



