In one case, where the circulation did not extend to another animal, one channel only was observed to be open in the peduncle, and in this a small current ran to and fro accord ing to the direction of the impulse given by the heart. Some animals, which had probably been injured, but were still connected with other vigorous ones, seemed to be in course of absorption. One was observed in which the soft parts were so shrunk as to occupy a small part only of the tunic. The currents of its peduncle extended into this mass, but no heart or motion of branchim was visible. Upon looking at the same the next day, the tunic was empty, the soft matter and the cir culation reaching only to the end of the pe duncle. Mr. Lister also once noticed a flux and reflux of the blood in a creeping stem, where the current did not communicate with any animal. In the buds sprouting from the stem, and destined to become new animals, the two streams of the stem run through the germ before its organs are developed.
The generation of the Clavellinidx takes place in two ways—by ova and by buds. The genesis of the lame of Clavellina from the ova is very similar to that of the larval Ascidite. The young of Perophora have not yet been observed. The method of the gemmiparous reproduction, according to the observations of Milne-Edwards, is as follows : Amongst the radiciform processes springing from the base of the test of Clavellina, and tending to preserve the animal in its position, are other filamentous prolongations which are hollow, and enclose a membranous tube, continuous with the internal tunic of the animal, and through which the circulation seen in the in terior of the abdomen is also continued. This stolon-like body is closed at the free extrem ity ; it is at first simple, but as it lengthens, it becomes ramified ; and when its growth is further advanced, there are developed on the extremities of its branches, and even at dif ferent points along its length, tubercles, en closing in their interior a minute organic mass connected with the interior tube. These
tubercles rise vertically, and become elongate and claviform. The blood that circulates in the stem at first penetrates into the soft, pear shaped, pedunculated mass occupying each of the tubercles ; but after a while these little germ-masses lose their peduncle and their at tachment to the internal tunic of the principal canal, and participate no more in the circula tion of the mother-animal. By further de velopment they soon put on the ascidian character. The branchial sac is perfectly dis tinct, although not yet communicating with the exterior ; and the digestive tube bent loop-wise, below the thorax, is plainly discern ible. Lastly, the oral orifice appears, and the general form of the young animal approaches more and more that of the adult. From this a new individual is then in like manner pro duced by stolon and bud, remaining attached to the mother by the former, and which at first has a circulation in common with the older animal, but soon enjoys an independent existence. The individuals either remain at tached by the intermediate root-like prolonga tions, or become separate by the disunion of these slender filaments.
In one species of Clevellina, the bud-like bodies and young animals are produced not only on the root-like stolons, but also on the walls of the test itself (fig. 768. u, u').
In Perophora the growth of the buds is con fined to the extremity of the creeping, root like tube, and the attachment of the indi viduals by the common root-stem is perma nent through life, and not merely existent during the young state.