478 Miscellaneous. 



alea, Cleodora, Tiedemannia, and Pneumodermon. In all, with the 

 exception of Pneumodermon, the development of which has been de- 

 scribed by Miiller (Monatsbeiicht der Kon. Akad, derWiss. zu Berlin, 

 October 1852), and by Kolliker andGegenbaur (Zeitschrift fiir Zoo- 

 logie, Bd. iv.), an oval embryo is formed, furnished with membranous 

 ciliated lobes (velum) and a shell (even in Firold). In the Pteropoda 

 this velum is persistent, and becomes transformed into the finlike 

 lateral appendages of these animals. In the Heteropoda, on the con- 

 trary, it gradually disappears as the animal acquires its characteristic 

 form. The velum of the Heteropoda and Pteropoda corresponds ex- 

 actly with that of the Gasteropoda, from which it follows that the 

 lateral lobes or fins of the Pteropoda, which are only an ulterior 

 metamorphosis of the velum, cannot be compared with the foot of the 

 Gasteropoda, as was Cuvier's opinion. 



2. Lastly, the author has ascertained that in many Mollusca the 

 generative organs contain both eggs and spermatozoa. The excretory 

 canal of these organs is not double, or furnished with two semi-canals, 

 as was supposed oy Meckel, but contains at once eggs and s))erma- 

 tozoa : this was shown by H. Midler of Wurzburg to be the case in 

 Phyllirho'c. — Comptes Rendus, Sept. 26, 1853, p. 493. 



TEETH OF TESTACELLUS AND GLANDINA. 



M. Moquin-Tandon, in the 'Journal de Conchyliologie ' (ii. 125), 

 describes the teeth of Testacellus, and among other particulars states 

 that the animal has no horny jaws, a retractile proboscis, and is car- 

 nivorous. 



M. Morelet (in vol. iii. pp. 27 & 257) and M. Raymond (in vol. iv, 

 p. 14 of the same Journal) describe the animal of two species of 

 Glandina from America and Africa as having nearly similar teeth, 

 a retractile jiroboscis without a horny jaw, and the same carnivorous 

 appetite. The latter author considers Testacellus as " a Glandina 

 with a rudimentary shell." Dr. Wyman described and figured the 

 teeth of Glandina in the ' Boston Journal of Natural History,' show- 

 ing them to be of a conical form. 



I intended, in my paper on the Teeth of Pulmonata in the last Num- 

 ber, to have observed, that the illustrations of that paper were kindly 

 drawn by Mr. S. P. Woodward from the well-mounted specimens of 

 Messrs. Cocken and Wilton. The examination of the large series of 

 mounted specimens belonging to these gentlemen and other micro- 

 scopists, has been very useful to me in these researches, as showing 

 the uniformity and permanence of the characters afforded by the teeth, 

 and sometimes of drawing my attention to peculiarities of form, and 

 inducing me to examine the teeth of the animal they were said to be 

 taken from. — John Edward Gray. 



On the Structure of the Retina in Man. By Profs. Kolliker 

 and H. MUller. 



The retina is composed of different layers — viz. 1. the layer of 

 cylinders and cones ; 2. that of nucleiform bodies ; 3. the layer of 



