384 



SCIENCE. 



[N. S. Vol. XXI. Xo. o32. 



TT „, I H. ftoridana {= H. mcxi- 



I cana). 

 Color mostly uniform seal- ' Color very variable. Shades 

 brown. of brown like seal, clove, 



Vandyke, etc., anil of gray, 

 cream, buff, etc. Often beau- 

 tifully marbled. Youug gen- 

 erally lighter. 



' Pits ' in skin. No ' warts.' ^ ' Warts,' each a heap of 

 spicules usually surmounted 

 by a conical papilla, gener- 

 ally present, especially in 

 young. No ' pits.' 

 Skin flaccid. 1-1.5 mm. , Skin firm, 2-5 mm. thick, 

 thick. 25 per cent, of dorsal 80 per cent, of dorsal append- 

 ambulacral appendag:es are ages are pedicels; of the 

 pedicels; the rest papillae. 5 remainder not all are true 

 types of calcareous end-plates ' papillse. Much larger per- 

 from large, well developed, ceutage of well developed 

 associated with the cylindri- end-plates, only 1 case of the 

 cal pedicels to small, vestigial , fourth and none of the fifth 

 with the conical papiihe. type. 



Calcareous rosettes like j Calcareous rosettes stel- 

 crosses; central rod elon- i late; central rod short; 

 gated. Longer, broader and | branches blunt. Twice as 

 more delicate. i thick as those of H. atra. 



Growth stages of the perfor- 

 I ated plates. 



Of 300 rosettes 2 had 3 holes. Special types of -J- and 8- 

 4 had 2 holes and 19 had 1 I hole plates, together with 

 hole. No well developed : other incomplete plates, are 

 plates. growth stages of the fully 



developed plates which have 

 I 4-31 holes; mean 13-14holes. 



The number and length of polian vesicles 

 and of stone-canals increase with age. 

 Seventy-one per cent, of the young H. 

 ftoridana have only 1 polian vesicle, M'hile 

 in the adult the number ranges from 1 to 

 92. The total number of stone-canals in 

 H. ftoridana ranges in the young from 2 

 to 25 ; in the adult, from 5 to 149. 



On Some Points in the Natural History of 

 the Oyster: Ramsay Wright, University 

 of Toronto. 



The author, who has been directing the 

 Marine Biological Station of Canada at 

 Malpeque, Prince Edward Lsland, during 

 the last two summers, exhibited some pho- 

 tographs in illustration of his paper. The 

 first showed that the kidney is a much more 

 conspicuous system of branched tubes, at 

 least during the spawning season, than is 

 generally supposed. The tubes extend in- 

 to the pericardial wall, and into the mantle 

 in the neighborhood thereof. 



Photographs of the male and female 

 genital ducts showed that it is possible in 

 ripe individuals to recognize the sexes with- 

 out examining the genital products. It 

 was stated that while in oysters of three 



or four years' growth the sexes are equally 

 divided, 90 per cent, of one year old oysters, 

 which are already sexually mature, are 

 males, a circumstance which seems to point 

 to the protandry which has been asserted 

 of the American oyster. A more exhaust- 

 ive study of this point is required. 



The occurrence of Urastoma (better, 

 Urostoma) cyprina, Graff, a commensal 

 turbellarian, was recorded from the oyster. 

 It has hitherto been obsei'ved in Cyprina 

 islandica from the Baltic, Mytilus ednUs 

 from the White Sea, and in Solen vagina 

 from Trieste. 



Diversity in the Scutes and Bony Plates of 

 Chelonia:* R. E. Coker, Johns Hopkins 

 University. 



I. Scutes. — There is a remarkable degree 

 of diversity in the number and arrange- 

 ment of the scutes of the carapace and 

 plastron of certain species of Chelonia, 

 notably Malaclemmys centrata (Latr.) and 

 TJtalassochclys caretta (L.). Of 244 speci- 

 mens of Malaclemmys, 109 were abnormal 

 in scutes; 20 per cent, had either more or 

 less than the typical number of carapace 

 scutes. About one half of the abnormal 

 specimens were asymmetrical. 



Neither in observations on Malaclemmys 

 nor in those on 26 embryos from a single 

 nest of Thalassochclys, was support found 

 for Gadow's theory of 'orthogenetic varia- 

 tion.' For example, the embiyos averaged, 

 per carapace, a fraction less than the typ- 

 ical number of scutes. 



Rare instances are found of a peculiar 

 form of variation that may be termed 

 'orthogenetic' 



II. Correlation. — The normal correlation 

 of scutes and plates is, roughly, a modified 

 alternation, the alternation being especially 

 simple in the marginal series. The corre- 



* Presented with the permission of Hon. Geo. 

 M. Bowers, U. S. Commissioner of Fish and 

 Fisheries. 



