S6 



HARD WICKE'S SCIENCE- G OS SIP. 



NOTES ON NAIADES. 



IN number 239, p. 261, Mr. W. Gain records the 

 taking of some large examples of Unio 

 pictorum, 4}-! in. long (I take the length as from umbo 

 to front margin, analogous to the apex and lip of a 

 gasteropod, not as taken by Mr. Gain) and asks 

 whether that size has been exceeded. I can answer 

 him in the affirmative. I have in my cabinet some 

 Unio pictorum, the dimensions and weight (Avoir.) of 

 some of them being as given below. 



in. in. oz. 



2 i6 X 5 = 2\ over. 



2 tb x 5 = 4 nearly. 



2 X 5ts = 3i over. 



2^ x si = 31 



2 is X 5+ = 3* over. 



These are careful, fair measurements, the weight 

 .not being given exact in every case, as will be seen. 



The shells are clean and beautifully grown, with 

 little erosion even on the umbones, and, so far as my 

 knowledge goes, they are the finest of their kind 

 ever seen. The following are Unio tumidus, 



in. in. oz. 



2^ X 4^ = 5i 



2 16 X 4'i = 5f nearly. 



2| X 4 = 5 over. 



2l X 5 = 5f nearly. 



Both the species occur in a pool near Birmingham, 

 which may fairly be called dirty, having the muddiest 

 basin I ever saw, with abundance of decaying vege- 

 table matter. 



I think I may answer for the accuracy of Mr. Gain's 

 identification of the species, which is also confirmed 

 by Mr. J. W. Taylor ("Jour, of Conchology," No. 4, 

 vol. vii. p. 224). This, for the satisfaction of Mr. E. 

 Harmer (Science-Gossip, No. 240, p. 280). 



In order to make this a little record of giant Naiades 

 let me note the following : — ■ 



In Science-Gossip, No. 43, p. 160, Mr. W. Ham- 

 brough records two fine shells of Anodonta cygnea, 

 taken at Worthing, of the following dimensions. 



7^ in. X 45 in. and 8 in. X 5 in. 



(The shells are measured as Mr. Gain's — the longest 

 way being taken as the " length.") 



No. 125, p. 11S, Mr. A. W. Langdon, of Hastings, 

 gives the size of a Southampton shell of this species 

 as 75 inches wide. 



No. 126, p. 136, Mr. Sclater crowns all, by record- 

 ing two of the largest shells of which I have heard, one 

 being 85 inches wide, the other over 9 inches wide, 

 both from the river Dart. It would be interesting to 

 know whether these fine shells are still in existence, 

 and to have their portraits. 



No. 129, p. 212, Mr. W. Budden gives 7 inches as the 

 width of a shell in his possession taken near Ipswich. 

 The largest shells I have from this neighbourhood are 



6£ in. wide. All the widest shells among the 



Unionidre I have seen have occurred in pools, the 



placid and even conditions of their life enabling them 



to increase the size of their shell, while in rivers and 



streams they rather increase it in strength, the usually 



rough pebbly or coarse sandy bed in which they live, 



being inimical to their expansive growth. I have a 



grand shell of the variety incrassata {A. cygnea) sent 



to me some years ago by Dr. Buchanan White, which 



weighs 7 oz., an extraordinary weight for this species ; 



an average shell of the same superficial measure would 



weigh under \ oz. Like Unio margaritifer, with 



which it dwelt in the river Earn, it had to construct 



a house which would withstand the knocking of stones, 



and it has successfully done it, coming out of the 



conflict scathless — here is beautiful adaptation. I have 



much to say about my old friends the Naiades, which 



I hope to have an opportunity of saying "some 



day." 



I am pleased to see the growing interest taken in 



conchology as evidenced by the frequent notes in your 



columns. I remember the time when they were few 



and far between. 



G. Sherriff Tye. 



Ilandsworth, near Birmingham. 



JAPAN WHITE, OUR WHITE BUTTERFLIES 

 IN JArAN. 



By the Author of " Insect Variety." 



I SEE from my window a white butterfly fluttering 

 and settling on the cabbage beds. She scents 

 each leaf over with a quick electric touch from the 

 knobs of her antenna;, and when she is persuaded she 

 is right, the extremity of her body is depressed with a 

 spasm, and a melon-shaped egg remains glued to the 

 spot. Once upon a time the white butterflies had 

 only the wild cruciform flowers to resort to, and it is 

 evident that the increase of cabbage culture has 

 multiplied their numbers in Europe, for in northern 

 Spain they are not nearly so abundant in the fields as 

 the Bath whites, nor in Italy are they as common as 

 the black veined, and in these countries cabbages do 

 not in the same degree populate the wilderness. The 

 green vein, on the other hand, has no sense for the 

 alien vegetation of the garden, and is still a wild 

 butterfly. To purloin her eggs you must go down to 

 the inky pool mantled over with water-cresses, and 

 watch there until a vagrant piece of white calico 

 comes dabbling in the mire, or you must track her 

 whims on the chalk cliff where the scentless mignonette 

 shoots rank. She is yet wild as the wolves, and has 

 none of the cat and poodle nature of your cabbage 

 whites. 



I have reared both the small white, and the green 

 vein from the egg. Until they attain the length of 

 seven lines there is little to discriminate the two 



