FISH. 59 



LETTER XVIII. To T. PENNANT, Esa. 



DEAR SIR, Selborne, July 27, 1768. 



I RECEIVED your obliging and communicative letter of June the 

 28th, while I was on a visit at a gentleman's house, where I had 

 neither books to turn to, nor leisure to sit down, to return you 

 an answer to many queries, which I wanted to resolve in the 

 best manner that I am able. 



A person, by my order, has searched our brooks, but could 

 find no such fish as the gasterosteus pungitius: he found the 

 gasterosteus aculeatus in plenty.* This morning, in a basket, I 

 packed a little earthern pot full of wet moss, and in it some 



twenty-five." J en . Brit- Vert- p. 295. I believe the habits of the whole genus may be very safely 

 inferred from those of onr common L- agilis, which are almost too well known to require descrip- 

 tion. They are thus concisely summed up by Mr. Jenyns : Fond of basking in the sunshine, and 

 in warm weather is extremely active. Forms a retraat under ground, in which it resides wholly 

 during winter. Is first seen in March, or early in April. Feeds principally on insects. Is ovivi- 

 parous, the young broods appearing in June or July. Tail extremely brittle, but, when broken, 

 gradually reproduced; the renewed part, however, according to Duges, never acquires vertebrae." 

 When under the full influence of sexual excitement in summer, the basal part of the tail, in the 

 male, is very much swollen, appearing as if the tail had been cut off and then set on again. In 

 this state it is the L- cedura of Sheppard, an identification first pointed out by Mr. Gray, and 

 acceded to by Mr. Jenyns, and which a series of intermediate specimens now before me sufficiently 

 demonstrates. In conclusion, let me hope that this desultory notice will at least tend to call the 

 attention of some readers towards the investigation of these neglected animals. 



Of the third order of reptiles, ophidia, but three British species appear to exist; the brittling, 

 or " slow-worm" (anguii fragilis) , of the family anguidcB ; and the ringed snake (natrix torquatus); 

 and common viper (vipera vulgaris), of the family serpentida- A- eryx, Lin., is probably a mere 

 variety of the first, JV. dumfrisiensis most probably an immature variety of the second, and the 

 " red viper" (colubu cherseaof Linnaeus) is believed to be only a variety of the common one, which 

 gradually loses its red colour as it increases in size. Black individuals of the common viper some- 

 times occur, but these do not constitute a distinct species. ED. 



* There is considerable difference of opinion among the first naturalists as to the number of 

 species of these minute fishes, Mr. Yarrall admitting as many as six different fresh-water kinds 

 to be found in Britain, while the Rev. L. Jenyns, reduces the number to three, and indeed hesi- 

 tates about admitting more than two, from a consideration of the very great tendency of gas- 

 terosteus aculeatus to vary, and this not only in the number of bony plates along the sides, but in 

 general contour and relative proportions, size and shape of the different erectible spines, magni 

 tude of the eyes, &c. See., some curious and surprising instances of whi?h are mentioned in his 

 work on the British members of the class vertebrata- I am myself disposed to concur in the latter 

 opinion, having repeatedly noticed the most remarkable and striking diversities between speci- 

 mens from different localities, which agree in the number of lateral osseous plates, and other 

 assumed specific characters. The curious reader is however referred to Mr. Jenyns' Manual, to 

 Mr. Varrell's admirable publication on British fishes, and above all to the ponds and brooks in 

 hii neighbourhood, personal research being by far the most satisfactory means of solving diffi- 

 culties and disagreements of this kind. I append descriptions which may probably assist the 

 enquirer. 



