106 LECTURE VI. 



in a narrow straight canal, which is continued into the inverted 

 pyramidal appendage, or bursa, attached to the hinder extremity of 

 the body, from which the single spiculum projects. 



In the Strongylus gigas the blind beginning of the testis is usually 

 found in the anterior half of the body, as at e {fig. 44.), the tube 

 descends into the posterior half, and is disposed in a number of long 

 coils, reaching from near the head, e', to the tail. One part of the 

 canal is wider than the rest, and forms a kind of seminal reservoir. 

 The terminal portion, f, is slender. The bursa or sheath of the penis 

 forms the posterior extremity of the body, and is a cutaneous produc- 

 tion of a round, expanded form, d, with the spiculum e, projecting from 

 its centre. In other species of Strongylus, as e. g. Strong, injiexus, 

 the bursa penis is bifid, and the intromittent organ is double : both 

 divisions are of great length in the Strongylus paradoxus : in the 

 Strongylus armatus the bursa is quadrifid. The SpiroptercB are dis- 

 tinguished 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 tli£ 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 gradually 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. 

 In the Ascaris mystax the basal half of each long and slender penis 

 is tuberculate for the attachment of its protractor and retractor 

 muscles : the apical half, which alone is protruded, is a slender 

 transversely striated horny spiculum. Accessory parts to aid mecha- 

 nically in the coitus are added to some of these limbless vermiform 

 parasites. In the Ascaris mystax, e. g., there is on either side of the 

 concavity of the caudal end of the body a tubercular ridge supporting 

 a membrane which is finely serrated, and gives a secure hold when 

 the tail of the male is wound round that part of the female's body 

 where the vulva is situated. 



The first steps in the development of the spermatozoa of the Neraa- 

 toidea have been well observed by Siebold * in the Ascaris paucipara, 

 a species favourable for this kind of research, on account of the large 

 size of the sperm-cells. The blind end of the tubular testis is occupied 

 by cell-nuclei (zellenkerne) with their nucleoli (kernkorperchen). A 



* XXIV. p. 153. 



