704 THE ANATOMY OF BOTIIRTOCEPHALUS LATUS. 



their course, so that Eschricht described them as a special structure, 

 the so-called " knot." The canal of this coil usually contains only a 

 single row of ova, including, however, also numerous free-yolk 

 granules, which indeed are so abundant that the coil acquires thereby 

 a more or less dark appearance. This is especially true of the outer 

 end of this coil-tube, which has usually the form of a spindle-shaped 

 sac (0'06 mm.), lying sometimes to the right, sometimes to the left 

 of the middle line, and which is the portion of the uterus where the 

 eggs acquire their hard shell. This is due to the fact that the 

 terminal portion not only receives the above-mentioned (p. 701) 

 fertilising canal, but also communicates with the efferent ducts not 

 only of the ovary and of the yolk-gland, but also of the shell -gland 

 (Fig. 366). 



The observation of this terminal portion is exceedingly difficult, 

 and the reports of investigators differ considerably as to its relations. 

 My enquiries have led me to conclusions which agree most closely 

 with those of Sommer and Landois ; the differences of opinion being 

 chiefly on subordinate points. They concern only the mode of con- 

 nection between the different portions, that such a connection does 

 exist, and that it is effected by the terminal portion of the uterus, has 

 been allowed by all observers since Eschricht. 



The Fertilising Canal will first be considered ; as we know it 

 extends from the dilated lower end of the vagina (the receptaculum 

 seminis), and which has the function of supplying the uterus with 

 the semen necessary for the fertilisation of the ova. For this pur- 

 pose this canal affords direct communication between the receptaculum 

 and the terminal portion of the uterus. It is a comparatively short 

 duct, which describes in the median plane of the joint a curve open 

 anteriorly. The longer limb, which descends on the ventral side, and 

 first receives the semen, has only an inconsiderable thickness (0*015 

 mm.), so that it is sharply and definately separated off from the 

 receptacle. Sommer and Landois have described it it seems to me 

 erroneously as extremely delicate, since a muscular sheath is 

 distinctly recognisable. It is internally lined by a relatively compact 

 cuticular membrane. Before this descending limb reaches the point 

 where it bends round, it receives the common oviduct, just as we 

 have seen (p. 445) in the fertilising canal of Tcenia. At the same 

 time it widens, so that Sommer and Landois regard it thenceforward 

 as a direct continuation of the oviduct. Shortly after receiving the 

 latter, the fertilising canal describes the above-mentioned loop-like 

 bend, and becomes again narrower, until after a short course 

 it passes into the terminal portion of the uterus, which is dilated 

 again here. 



