SQ Zoological Collections. Invertebrata. 



is covered with little cartilaginous spots, is neither attached to the integument 

 nor to the internal membrane, whence there are two cavities, one between the in- 

 tegument and the external membrane, and another between the latter and the 

 internal membrane. The former cavity communicates with the air by means of 

 a transverse groove in the integument, which has been noticed by Redi, near the 

 anterior extremity of the animal. The internal cavity also communicates with 

 the air by apertures which open alternately in the interstices of the feet. 



The external membrane is continuous with the tunic which covers the exterior 

 of the ventral surface. The dorsal integument does not extend below the feet. 

 The internal membrane of the back is continuous with the internal ventral tunic, 

 which is formed of muscular fibres decussating in every direction, and which is 

 entirely distinct from the external ventral tunic, so that there is also a cavity be- 

 tween the two membranes of the lower surface. This cavity also communicates 

 with that formed by the dorsal membranes, whereby the water has a free circula- 

 tion in the interstices of the double envelope of the animal. 



But this general cavity also communicates with the interior of the abdomen 

 by two grooves, opposite the openings which occur between the feet, as abov6 

 mentioned. The water is thus able to penetrate into the intestinal cavity, and 

 we have an explanation of that which Pallas could not understand, how the ova 

 are transmitted into the interstice of the double envelope, and thence passed from 

 the animal. 



Hitherto the generative organs of the Aphroditae have been unknown. M. 

 Treviranus thinking that he has discovered the ovaries in two series of little 

 bodies, lying in the cavity of the abdomen, along the external margin of each 

 longitudinal ventral muscle ; these corpuscles have an obtuse rounded extremity 

 attached to the muscle, and a pointed extiemity which is free. Near the blunt 

 extremity there arises a little canal, which is lost in the abdominal cavity. Each 

 corpuscle contains a yellowish fibrous matter. 



M. Treviranus is of opinion that the respiration of the Aphrodite is carried on 

 by means of capillary vessels with which the coecal appendages of the intestinal 

 canal are supplied. And this is the more easily conceived that the water has ac- 

 cess to the abdominal cavity as above stated. This view receives additional pro- 

 bability from the Amphinomts, which are nearly related to the Aphroditce, having 

 ho capillary vessels on the coeca, whilst they possess external branchiae, exactly 

 resembling the capillary distribution on the cceca of the Aphroditce. Thus the 

 only distinction between these two genera, in respect of the respiratory apparatus, 

 is, that in one it is external, whilst in the other it is carried on in the abdominal 

 cavity. 



The dorsal plates, which have been considered to be the organs of respiration, 

 couid not, according to M. Treviranus, perform that function, since they contain 

 ho blood-vessels ; they are only rudimentary branchiae {Zeitschrifi fur Phy- 

 siologies III. Cah. 2. p. 157.) Bull, des Sci. Nat. xxi. 165. 



The Eyes of Mollusca.—Many physiologists have doubted if the black dots, 

 which are seen on the tentacula of mollusca, are real eyes ; and some have even 

 denied that they are used for vision. These doubts may have been occasioned 

 by their having examined snails (helices) and terrestrial mollusca, where these 

 organs are only very imperfectly developed ; but if they had examined the eyes 

 of the marine carnivorous mollusca, Buccinum undatum, or Fusus despectus, 

 and more especially some of the larger Strombi, they would have found the eye 

 as fully developed as in the cuttle-fish, (Sepia,) showing the cornea and the nearly 

 orbicular crystalline lens almost perfectly formed, as may be seen by any person 

 simply cutting the cornea across, and slightly pressing it, when the crystalline 

 lens will protrude. It is curious that Cuvier, in his anatomy of the welk, (Ann. 

 Mus.) should have overlooked this fact J. E. Gray. 



The Animals of Calyptraea, Capulns, and Crepidula The anatomical exa- 

 mination made by Mr. Collie, the surgeon of the Blossom, during his voyage 



