134 HELMINTHOZOA. 



On the sides of the body, extending nearly its whole length, are two 

 slender and slightly flexuous tubes (fig. 69, n n), whose presence it is 

 difficult to detect when in an empty condition, but which generally con- 

 tain in their interior vitelline globules closely aggregated together, 

 which by the peristaltic movements of the tube, aided by ciliary action, 

 are forced onward from before to behind. The two vitelligenous tubes 

 ultimately unite to form a common canal (n), situated near the median 

 line, through which the vitelline globules enter the germiduct at the 

 point marked ra. On passing the opening of this canal, the germ be- ' 

 comes suddenly invested with a layer of vitelline globules, and, being 

 thus transformed into an ovum, is carried onwards through the flexuous 

 canal, or proper oviduct (p), into the matrix (^), becoming invested in 

 its passage through the oviduct with an outer covering that represents 

 the egg-shell. 



The matrix (q) thus receiving a continual supply of ova, becomes 

 gradually distended, until it occupies almost all the interior of the body, 

 and branches out in different directions into caecal pouches at points 

 where the least resistance is offered, until finally the skin of the 

 proglottis becoming as tightly distended as the matrix, both are 

 ruptured, and the ova escape in this artificial manner. The vagina 

 (fig. 69, g g) is a large canal, having, like all the organs belonging to 

 this apparatus, distinct parietes. It commences externally (/) in the 

 immediate vicinity of the male organ, penetrates to the centre of the 

 body, and, bending at an angle, makes its way backwards to the space 

 that separates the two ovaria (germigenous organs, i). Its length is in- 

 variably in correspondence with that of the penis of the male apparatus. 

 At the extremity of the vagina is situated the copulative sac (h), a 

 small vesicle with very delicate parietes, the contents of which abound 

 in spermatozoa. 



Such being the anatomical arrangement of the different parts of this 

 somewhat complex apparatus, it now remains to take a brief survey of 

 their physiological import in the performance of the generative function. 

 In the living Entozoa it is sometimes not difficult to see the germi- 

 genous and the. vitelligenous organs opening into a common canal, and 

 each of them pouring their product into its cavity ; and if a specimen 

 is selected in which the parts are in full activity, and the compression 

 used be such as to render the organs transparent without putting a stop 

 to their action, the germs may be seen to arrive, one by one, at regular 

 intervals, before the opening of the vitelligenous organ, which, contract- 

 ing forcibly, expels a certain quantity of the vitelline substance, in which 

 the germ becomes enveloped, having previously, on passing the orifice of 

 the copulative sac, become impregnated by contact with the sperma- 

 tozoa therein contained. As the vivified ovum advances onwards it 

 receives its outward envelope, arrives in the matrix, and is there re- 

 tained until birth is accomplished by the destruction of the animal. 



