Johannes Fibiger and Hjalmar Ditlevsen: Spiroptera neoplastica n. sp. 21 



more caudal in the animal than shown in the figure. However, it has proved impossible 

 to state exactly the most posterior limit. Each of the spicules is surrounded by a sheath, 

 the surf ace of which seems to consist of a chitin-membrane; on examination with immersion 

 (apochr. 2 mm.) it presents a most peculiar spotted surf ace, each spot being due to a dimi- 

 nutive circle and most Hkely representing holes or grooves. Somewhat more caudally 

 situated, not far from the distal end of the thicker spicula, another piece of sheath is 

 found, the object of which possibly might be to make the two spicules keep their 

 distance and to support the whole sheath-apparatus. The latter piece seems bigger 

 and more thick-walled than the sheaths which compass each spicule. A faet which 

 renders it difficult to accomplish an examination of this part of the worm, is the 

 highly developed muscular system which is found here. 



From the neighbourhood of the anus, broad muscular bands arise, running 

 partly ventrodorsally on each side of Rectum and Ductus ejaculatorius, partly obliquely 

 forwards, partly obliquely backwards or flabelliform towards both sides. 



The interior genital organs are found corresponding to the usual type. The testis 

 being single presents quite a straight line with no curvings, and almost reaches as far as to 

 the proximal end of the oesophagus, where it turns, running back in caudal direction, 

 parallel to itself, and terminating in a small retort-shaped dilatation. The returning 

 branch is always quite short (PI. IV fig. 29). In exceptional cases the course may be 

 somewhat different, f. instance when after returning the testis turns once more, and 

 for a little while takes a cephalic direction, after which it terminates in the usual 

 way, bent caudal. In no specimen was the testis found surpassing the limit between 

 the oesophagus and the intestine. Usually the point of turning will be at a distance 

 of c. ^2 mm. from the said limit. The testis does not vary in width, the minimal 

 diameter being near to the turning where it measures 24«. In the middle of its 

 length it is about 60 fi and its maximal width is found to be 72 p.. The hind part 

 of the genital duet presents a differentiation; posterior to testis it narrows to a 

 narrow duet, which evidently serves as nothing but a conduct-pipe, and there- 

 fore may be pointed out as Vas deferens. It is c. 70 // in length, although no 

 exact measure can be given as seen from flg. 27 PI. IV; the distal end of the testis 

 is tapering evenly into a conical part, which passes into the vas deferens without any 

 distinct line of demarcation. The vas deferens then again increases evenly in width 

 and passes into a dilated part reaching towards the anus, nearly in front of which 

 it narrows into a short Ductus ejaculatorius. The dilated part which is to be 

 marked out as vesicula seminalis has a length of a little more than one mm. and 

 often is brimful of spermatozoa. When placing the worm alive under the cover-slip 

 the spermatozoa often by the pressure may be forced out through the anogenital opening. 

 They then appear as small regular globular-cells. 



