62 LEUCKART, ON DEVELOPMENT OF ECHINORHYNCHUS. 
the proboscis-sheath, in consequence of which it gradually 
acquires a club-shape. 
When the young worm has reached the length of from 
0:4 to 0°-45mm., or about half that of its parent, a space 
becomes perceptible between the integument and the viscera, 
and which represents the commencement of the visceral 
cavity. This space is widest and most distinct in the annular 
segment between the sheath of the proboscis and the ligament. 
And in this situation may now be perceived in their proper 
places on either side, a pair of short and thick retractor 
muscles, extending in a straight line from the end of the 
proboscis-sheath to the contiguous wall of the body. And 
about this time, I think, may be observed the first traces 
ot certain differences in the position and form of the internal 
sexual organs, which may be taken, I conceive, to indicate 
a sexual difference. 
Up to this stage the anterior and posterior half of the body 
have continued to grow pretty nearly in an equal ratio. But 
now the growth of the latter begins more and more to pre- 
ponderate. The points of insertion of the retractor muscles 
recede further and further backwards, and the suspensory liga- 
ment, which at first could hardly be distinguished as an inde- 
pendent structure among the crowded parts constituting the 
sexual apparatus, becomes more and more evidently the sup- 
porter of those organs. In its uppermost part, two oval 
swellings may be perceived in it, which partially overlap each 
other, and represent the first rudiments of the male and 
female reproductive glands, as the case may be. Some way 
behind these is a short, cylindrical portion, surrounding the 
lower end of the ligament like a sort of sheath. In the 
female this is the first rudiment of the so-termed uterine-bell or 
tube. Inthe male, in which from the first it has a somewhat 
different aspect, it becomes afterwards the vas deferens and 
vesicula seminalis. Posteriorly this median organ terminates 
in an almost spherical end, at this time nearly completely en- 
veloped by the muscular wall of the body ; and which, in the 
male, becomes more and more evidently recognisable as the 
rudiment of the bell-shaped penis, whilst in the female it is 
transformed into the vagina, whose upper end is not de- 
veloped into the elongated, so-termed “‘ uterus,” until after- 
wards, as the time of sexual maturity approaches. 
The preponderating growth, both in length and thickness, of 
the posterior half of the body continues to be more and 
more manifest, so that the anterior segment, with the pro- 
boscis-sheath, and proboscis-cavity, which now reaches as far 
as the ganglion (but little increased in size), acquires more 
