ENTOZOA. 73 



a round, enlarged, truncated form, with the spiculum projecting from 

 its centre, as at fig. 30. In other species of Strongylus, as in the 

 Strong, infiexus, the bursa penis is bifid, and the intromittent organ 

 is double. In the Strongylus armatus the bursa is quadrifid. The 

 SpiroptercB are distinguished by the aliform membranous caudal 

 appendage in the male. 



In the Ascaris lumbricoides the penis projects from the anterior 

 part of the anus in the form of a slender, conical, slightly curved 

 process, at the extremity of which a minute pore may be observed 

 with the aid of the microscope. The base of the penis communicates 

 with a seminal reservoir, and is attached to several muscular fibres, 

 destined for its retraction and protrusion : the reservoir is about an 

 inch in length, and gi-adually enlarges as it advances forwards : the 

 testis or seminal tube extends to the anterior third of the body, 

 forming numerous convolutions or loops about the intestine : its 

 attenuated caecal extremity adheres closely to the dorsal wall of the 

 abdomen. The total length of the seminal tube is about three feet. 

 The essential part of the fluid consists of nucleated cells, which, in 

 the Ascaris lumbricoides, present an irregular, triangular, sub-com- 

 pressed form. In the Strongylus they are subspherical, with a clear 

 nucleus ; but undergo, according to Dr. Bagge *, a marked change of 

 form when introduced into water ; they then become elongated, and 

 assume a wedge-shape. 



From the examples which have been adduced of different genera 

 of the Nematoidea, we may perceive that although there are many 

 varieties of structure in the copulative part of the male generative 

 apparatus, the essential or secerning portion uniformly consists of a 

 single tube. A like uniformity of structure does not obtain in the 

 essential parts of the female organs : in a few instances the ovary 

 is single, corresponding to the testis in the male, but in the greater 

 number of the nematoid worms it consists of two filamentary tubes. 



The Strongylus gigas is an example of the more simple structiu-e 

 above alluded to. The single ovary commences by an obtuse blind 

 extremity close to the anal extremity of the body, and is firmly 

 attached to the termination of the intestine ; it passes first in a 

 straight line towards tlie anterior extremity of the body, and, when 

 arrived to within a short distance from the vulva, is again attached 

 to the parietes of the body, and makes a sudden turn backwards ; it 

 then forms two long loops about the middle of the body, and returns 

 again forwards, siuldenly dilating into an uterus, which is three inches 

 in length, and from the anterior extremity of which a slender cylin- 



* Loc. cit. p. It?. 



