LEUCKART, ON DEVELOPMENT OF ECHINORHYNCHUs. 61] 
Without going into minute particulars with respect to the 
transformation of the cellular mass in the Echinorhynchus, 
still a few words may be said regarding the most important 
points concerned in this metamorphosis. 
As before remarked, this process commences in a defined 
and regular grouping of the cells which had previously been 
united into a simple ball. Next, it may be seen that the 
anterior end of the ball becomes defined from the rest, or 
rather, that in consequence of a clearing up in its interior, 
it is transformed into an almost lenticular vesicle, whose 
outer wall is constituted of a thin layer of cells, and is 
usually distinguished by a number of yellow granules. Sub- 
sequent observation will show that this transparent vesicle is 
the rudiment of the cavity of the proboscis. Behind this part 
will be seen an oval mass of cells of considerable size, extending 
backwards in the axis of the body to about the middle of its 
length, and in its posterior half enclosing a smaller, though 
still a considerably sized cellular body. This body ‘is the 
future ganglion, whilst its envelope represents the future pro- 
boscis-sheath. At the hinder end, again, of this part are 
attached, also in the axis of the body, several small collec- 
tions of cells, which are sometimes crowded together, some- 
times arranged one behind the other, in a longitudinal series, 
and which, together with the terminal portion of the nucleus, 
go to constitute the sexual apparatus together with the so- 
termed suspensory ligament. ‘The lateral walls of the middle 
portion of the body, bounded in front by the cavity of the pro- 
boscis, and behind by the terminal portion of the repro- 
ductive organs, and which, at first, are of very considerable 
thickness, are destined to form the future muscular tunic or 
sac of the Echinorhynchus. At this time no trace of visceral 
cavity is perceptible. 
The next changes in the young Echinorhynchus cousist in 
its continued and rapid growth in length to twice or thrice 
its original dimensions, without any increase in its transverse 
diameter. The growth is limited almost entirely, however, 
to the middle section of the body, or that which is sur- 
rounded by the lateral walls, and the form of this part con- 
sequently becomes more and more cylindrical as the growth 
proceeds. At the same time the walls of this part become 
thinner ; whilst the inclosed organs, the proboscis-sheath, 
and the sexual organs appended to the so-termed “ ligament,” 
notwithstanding all the stretching, retain their original 
plump form almost unchanged. The most remarkable 
alteration is the lengthening of the cavity of the proboscis, 
which continues to extend backwards deeper and deeper into 
