Miscellaneous. 487 
luted tube, which is closed at one end, and at the other opens 
externally on the ventral surface. This tube is the body-wall of the 
future worm. By becoming turned inside out it issues from the 
body, at the same time taking in the intestine of the larva completely. 
This process, considered in detail, is as follows:—The tube is 
swelled at its closed end into the form of an acorn. A little before 
this inflation, its outermost layer (the innermost layer of the per- 
fect worm) is firmly attached to the wall of the intestine of the 
Actinotrocha, at the spot where the stomach or middle part of the 
intestine passes into the rectum or terminal part of the intestine. 
In the meanwhile the vascular system of the worm is already formed. 
A narrow double streak, which runs along the dorsal surface of the 
stomach and cesophagus, is the foundation of the two longitudinal 
vessels. At the spot above mentioned, at the commencement of the 
rectum, numerous ceca sprout forth. These are the czecal diverticula, 
which, in the perfect worm, stand upon the posterior loop of the 
vessels. Although there is not yet any circulation of blood, these 
portions of the vascular system, and especially the czeca, are already 
in jerking motion. The anterior annular vessel, as also the blood- 
corpuscles, are produced from two aggregations of cells of a blood- 
red colour, which stand on each side of the anterior extremity of the 
tube. After these preparations, the tube turns itself out, in the 
manner of the tentacle of a Snail. As the intestine is attached to it, 
this is drawn out with it, like a loop of intestine in hernia. The 
entire body-wall of the larva disappears, with the exception of the 
tentacles, which, now contracted into a close circlet, close the anterior 
extremity of the tube. The oral lobe and rotatory organ have com- 
pletely disappeared. The mouth and anus remain the same, except 
that now they are brought quite close together, both standing at the 
anterior end on opposite sides. However, all the tentacles of the 
larva are not transferred into the worm. ‘Towards the close of the 
larval life, a second circlet of tentacles sprouts forth at the base of 
and behind the first circlet of tentacles. Only the second remains ; 
the first falls off. 
The entire surface is ciliated, with the exception of the hindmost 
acorn-shaped end. As far as the ciliation extends, a transparent 
tubular sheath surrounds the body. The free posterior extremity, 
which is set with small warts, serves the animal for attaching itself. 
The blood now circulates briskly : it streams forward through one 
vessel, enters the tentacles, and flows back through the other vessel. 
At the posterior end the two vessels are united by the above-men- 
tioned loop, beset with contractile czeca. 
The worm has not yet, however, attained its definitive form. 
The tentacles, together with the portion of the skin on which they 
are seated (the last-remaining portion of the body-wall of the 
Actinotrocha), are thrown off in a coherent piece, as in a moulting, 
By this means the anterior extremity acquires a button-like form. 
The circulation continues, but the vessels now pass into each other 
in a simple loop at the anterior end. The further development of 
the worm could not be traced. Monatsber, der Akad, der Wiss, zu 
Berlin, October 1861, p. 934. 34* 
