Invertebrata. Zoological Collections. 247 



The liver is large in the Cyclades. The organs of touch consist of the 

 tentacula already mentioned, and of the sensitive filaments which encircle 

 the tracheee. As to the nervous system, M. Jacobson easily distinguished 

 the first pair of nervous bundles situated behind the tentacula, and two 

 nervous fasciculi, which are prolonged on the sides of the belly. With 

 regard to the parts belonging to the organs of circulation, he could only 

 make out with certainty the form of the heart. The organs of respiration 

 in the Cyclades present several peculiarities. All the testacea have two 

 pairs of gills, which are commonly of the same size. In the Cyclades, how- 

 ever, M. Jacobson was struck, on opening them, by seeing that the external 

 pair is twice as long and broad as the internal pair ; but this is only because 

 the skin which attaches the pair to the belly of the animal is much advanced. 

 The intestinal canal runs along the upper margin of the gills ; it is more 

 distinct in the external than the internal ; the lower or convex margins of 

 the two pairs are scattered over with small points. 



With respect to the organs of generation, M. Jacobson could find only 

 the ovaria. They are situated on the two sides of the belly, and bounded 

 by the liver and the convolutions of the intestinal canal. Each ovary 

 is composed of a quantity of small sacs or cylindrical capsules, attached by 

 their pointed extremity to a strong pellicle in the interior of the ovarj'. 

 They touch by the other end the wall of the gills without being attached to 

 them. It is in these sacs or capsules that the foetus are formed. They 

 grow there, and, when come to maturity, rupture the sacs, and are let out by 

 a lateral opening, having the form of a crescent. The Cyclades bring forth 

 young during all the summer. We therefore find in the gills, young already 

 formed, and capsules which contain the growing foetus. The largest young 

 found in the gills are about one-fourth of a line in diameter. They are of 

 a white colour, and of a round and flattened form, and the foot protrudes 

 between the shells. They perfectly resemble the mother, except that they 

 are flat. They grow rapidly ; the shell assumes a yellow tint, and the 

 foot is gradually drawn in. When they are half a line in diameter, they can 

 close their shells perfectly, which at length assume a more convex form. 

 When the little ones have attained the size of a lentil, or one line and a half 

 in diameter, they quit the mother. Thus a quantity of these little ones is 

 found at the bottom of ditches. 



The author, at the end of his memoir, sums up his observations, reducing 

 them to four results, as follow: — 1. Among the acephalous mollusca there 

 are some which produce their young alive : the Cyclades are of this number. 

 2. The young of these animals resemble their mothers from the first, and 

 consequently undergo no metamorphosis: their belly is not slit or open : 

 their foot is only large in proportion to the shell. 3. They grow very 

 rapidly. 4. Their shell contains but little calcareous matter. — Bull, des 

 Sci. Nat. Oct. 1830. 



Polyzoa, a new animal discovered as an hihahitant of some Zoophytes.'^-- 

 In the last number of the Zoological Researches, Mr Thompson describes, 

 under the name Polyzoa, the animals of Sertularia imhricata of Adams ? S. 

 cuscuta, S. spinosa, and S. pustulosa. He finds the inhabitants of these 

 zoophytes to be totally different from those of the Campanularice, Plumularice, 

 and the genuine Sertularice of Lamarck, " which are undoubted Hydrce ,-" and 

 of this new form of animal, he remarks, that " while it must be allowed to 

 belong to a new type of the Mollusca acephala, it resembles exteriorly in 

 some measure the Hydra." For want of space, however, we must delay 

 farther notice of Mr Thompson's discovery until our next number. 



iiili tiiuiiii , 



