M. Van Beneden on a new genus of Cestoid Worm. 45 



larger at the base, where it is covered with asperities, and when 

 unrolled nearly equals the body in length. 



The lemniscus is also lodged in a sac resembling the sheath of 

 the tube of Tetrarhynchus, and unrolls itself like that tube. A 

 very perceptible retractor muscle arises from the bottom of the 

 sheath, and thence extends to the extremity of the lemniscus. 



We agree with Siebold, that, like as in the Trematoda, the 

 Nematoidea and other worms, there exists one organ for the for- 

 mation of the germ, and another for that of the vitellus. The 

 germigenitor (germigene) occupies almost the whole length of 

 one side of the body, having a coiled form, and is easily detected 

 when containing germs. 



The vitellogenitor (vitellogene) is made np of cells more or less 

 round, often very clear, and which are distributed throughout 

 the parenchyma in large number. Ova in their interior are often 

 to be seen in course of development. We believe that the cells 

 rupture, scattering the vitelline globules in the cavity of the 

 body, which then envelope the germinal vesicles after they have 

 undergone contact with the spermatozoa. 



A dull white organ is also seen in the centre of the body, 

 which, when the animal is compressed, appears a tortuous cord, 

 like the testes of insects. It has distinct walls, and may be com- 

 pletely uncoiled. We have supposed this tube might terminate 

 at the base of the lemniscus, but have been unable to determine 

 this opinion by observation. We regard this organ as the testes, 

 but do not think it discharges its product externally. 



In the interior of the body we have observed ova in course of 

 development, having experienced the action of the spermatozoa; 

 but as there is no perceptible opening externally, we are compelled 

 to admit fecundation to result from the spermatozoa of the same 

 animal, which implies complete hermaphrodism. 



Helminthologists generally admit the existence of natural 

 vents for the escape of the reproductive products, but, in the 

 worm described, nothing of the sort is seen. When the skin of 

 an animal, on the object-glass of the microscope, ruptures, the 

 ova escape through the rent. 



The ova are very small, measuring but y^yth of a millimetre, 

 but are not otherwise remarkable. It is worth while to observe, 

 however, the great difference in size the ova present in animals 

 closely allied. Thus in Bothriocephalus fios the ova at the time of 

 their discharge have eight or nine times the volume, and admit 

 of the ready observation of their cells in process of organization. 



Affinities. — The Echinobothrium is allied to the Bothriocephalce, 

 but cannot be included in that or any established genus. In 

 seeking to classify this worm we have been struck with the sin- 



