142 Analyses of Books. [Feb* 



has derived its strongest support from the absence of those 

 organs on the surface of the body of the animal in question, 

 which are found in all the shelled mollusca, and by which the 

 secretion of the calcareous matter forming the shell is effected. 

 Rafinesque, from his situation on the coast of the Mediterra- 

 nean, has had peculiar opportunities of studying this animal, and 

 is fully of opinion that it belongs to a genus nearly allied to the 

 sepia of Linngeus, to which he has given the name of ocythbe, and 

 resides, parasitically, in the above-mentioned shell. 



Some observations made by the late Mr. Cranch, zoologist to 

 the unfortunate expedition to the Congo, tending strongly to 

 confirm the theory of Rafinesque, are detailed by Dr. Leach in 

 the present paper. 



" In the Gulf of Guinea, and afterwards on the voyage, he 

 took (by means of a small net, which was always suspended over 

 the side of the vessel) several specimens of a new species of 

 ocythbe, which were swimming in a small argonauta, on the 

 surface of the sea. 



Two living specimens being placed in a vessel of sea-water, the 

 animals very soon protruded their arms, and swam on and below 

 the surface, having all the actions of the common polypus of our 

 seas. By means of their suckers they adhered firmly to any 

 substance with which they came in contact ; and when sticking 

 to the sides of the basin, the shells might easily be withdrawn 

 from the animals. They had the power of completely withdraw- 

 ing within the shell, and of leaving it entirely. One individual 

 quitted its shell, and lived several hours, swimming about, and 

 showing no inclination to return to it ; and others left the shells 

 as he was taking them up in the net." 



The same species which has furnished Dr. Leach with the 

 materials for this paper, has also afforded to Sir Everard Home 

 the subject of a short communication, tending to confirm the 

 opinion of Rafinesque. In some of the specimens of ocythbe 

 cranchii, the animal had deposited its eggs in the involuted part 

 of the shell which it occupied ; these eggs form a cluster, held 

 together by pedicles, one of which belongs to each egg, in this 

 respect resembling the ova of the sepia octopus. But the eggs 

 of all the testaceous aquatic mollusca, as far as they are known, 

 are enveloped in a gelatinous mass, which corrugates by the 

 action of the sea water, and thus encloses each ovum in a cell, in 

 which the young animal passes the interval, usually very short, 

 between its being excluded from the membranes of the ovum, 

 and its acquiring a shell. 



Dr. J. R. Johnson, of Bristol, has communicated some obser- 

 vations on the hirudo complanata, and hirudo stagnalis, the 

 object of which is to show that these animals differ from the 

 other known species of leech in such important characters as to 

 justify the arrangement of them in a new genus, to which Dr. J. 

 gives the name of glossopora. 



