Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
will, presently, be more particularly de¬ 
scribed. From this disposition it results that 
the contents of the stomach can pass as far 
as the extremities of these four vessels, and 
by means of the transverse canal can be trans¬ 
it. 50. 
A series illustrating the development of Tubularia ly 
free gemmœ, after the detachment of the embryo 
from its peduncle, in continuation of that in the 
preceding cut. The same letters indicate similar 
parts in all the figures in this and the preceding 
Fig. 1. An embryo detached and moving in the 
water like a Medusa, seen in profile ; in addition to 
the four vessels, whose development is demonstrated 
in the foregoing series, eight other canals (/) are 
now perceptible ; these belong to the external enve¬ 
2. The same viewed obliquely, showing the situa¬ 
tion of the mouth e ; h, the transverse canal which 
brings the four vessels into communication. 
3. The same seen from below. 
4. The four bands or vessels contracted a little, 
giving to the embryo a subquadrate outline ; viewed 
from below. The embryo is now no longer spheri¬ 
cal, but flattened, as well as subquadrate. 
5. The embryo viewed obliquely from above ; the 
superior and inferior parietes drawn together ; the 
stomach projecting through the mouth. It now 
presents the form of a Greek cross, owing to the 
great contraction of the longitudinal bands or ves¬ 
6. The embryo placed inverted with respect to Fig. 
1 ; the stomachal cul-de-sac, which becomes the 
body of the polype, completely protruded. 
7. An ideal transitory figure. 
8. The embryo become fixed. The internal row 
of tentacles beginning to protrude. 
9. The same more advanced. The two rows of 
tentacles further developed. 
ferred from one to the other. Professor Van 
Beneden observed a fluid containing globules 
moving in this direction in their interior. The 
communication between the longitudinal ves¬ 
sels and the stomachal cavity, and their inter¬ 
communication by means of transverse canals, 
is another arrangement exactly similar to what 
exists in the adult Medusae. 
The outer membrane presents eight longi¬ 
tudinal canals, which are found to be filled 
with cellules, but in which no movement has 
been observed. It is to the presence of these 
longitudinal bands that the embryo in this 
stage of its development owes its resemblance 
to certain fruits, more particularly to a 
From the anterior part proceed four ap¬ 
pendages (d), which were still undeveloped 
at the period of the detachment of the young 
polype, but which insensibly unfold them¬ 
selves. These are the tentacula. In the centre 
there projects a rounded opaque body (b), 
generally of a red or yellowish tinge, which 
is the stomach. This viscus communicates, 
as has been stated above, with the four lon¬ 
gitudinal vessels, and is the only opaque part 
of the embryo. It opens in front by an orifice 
which constitutes the mouth ; the whole 
organ is eminently contractile, turning itself 
in all directions like the body of a Hydra, 
sometimes elongating itself like a worm, and 
at others shrinking so as to be almost imper¬ 
If the embryos examined in this condition 
be vigorous, their movements are very varied, 
and the forms that they assume extremely 
singular. The regular contractions above 
noticed are the most simple actions ; the two 
poles separate and approach each other alter¬ 
nately, whence results the progression of the 
little creature. But this contraction may be 
carried to a still higher degree: the rounded 
stomach in the middle of the embryo not only 
contracts itself in every direction, but it seems 
to turn itself in the middle of' its transparent 
envelope like a worm in search of a passage 
by which to get out ; and at length it pushes 
its free extremity through the opening in front 
of it, and elongates its body still more until


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