PISH. 
59 
LETTER XVIIL To T. PENNANT, Esq. 
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 g aster osteus pungitius: he found the 
g aster osteus aculeatus in plenty.* This morning, in a basket, I 
packed a little earthern pot fuU of wet moss, and in it some 
twenty-five.'^ — Jew Brit' Vert- p. 295. I believe the habits of the whole genus may be very safely 
inferred from those of our common £. 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 vertebr^e.'^ 
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 sufliciently 
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" {anguis fragilis) , of the family anguidoe ; and the ringed snake {natrix torquatus)', 
and common viper {vipera vulgaris), of the family serpentidcB- A' eryx, Lin., is probably a mere 
variety of the first, N- dumfrisiensis most probably an immature variety of the second, and the 
' red viper" {colubu chersea of Linnseus) 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 diff'erence 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. &c., some curious and surprising instances of whi-;h are mentioned in his 
work on the British members of the class vertehrata- 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. Yarrell's admirable publication on British fishes, and above all to the ponds and brooks in 
his 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. 
