WCP2188

[1]¹

Zoological Society's Gardens,

Regent's Park,

London, N.W.

April 16 1886

My dear Sir

The only instance of a well marked series of structural variations in a given species known to me at first hand is in a species of earthworm — Perionyx excavatus (Perrier). Out of 2,000 examples I found 13 specimens showing eleven well marked variations.

The characters of the species are briefly as follows

Colour (in alcohol) reddish violet above dirty yellow beneath

Setae forming a complete row round each segment

Two pairs spermathecae — spherical pouches without diverticula — in segments 8 & 9. [2] Two pairs of testes in 11 & 12.

Ovary a single pair in 13.

Oviduct open by a common pore in the middle of segment 14

Vasa deferentia open separately on to 18 each furnished at its termination with a large 'prostate' gland.

The variations observed were (1) in the number of spermathecae (3 or 4 pairs instead of two) & in their position

(2) in the ovaries & oviducts; there were occasionally two pairs of ovaries each with its own oviduct; the external apertures of these varied in position [1 word illeg.] upon 13 & 14, 14 & 15 or 15 & 16. Occasionally when there was only the normal single oviducal pore present it varied in position (once on 10^th & once on 11^th segment)

(3) in the male generaratic pores vary in position from 14 — 20 — I found them in different examples on all of these segments. In one instance there were two pairs instead of the normal single [3] ²pair — in this case each of the four apertures had its own prostrate gland.

The above is a brief sketch of the variations I have noted; I would impress upon you the fact that all or nearly all of the above variations are found normally in other genera & species. For instance the genus Acanthodrilus has four male generatic pores. The genera Euclipidrilus[?] & Chretogartus[?] have been described as forming two or three pairs of ovaries.

I would also venture to suggest to you that the group of earthworm is one particularly favourable to showing variations such as are necessary to prove your & Darwin's views. They evidently have some relation —— as regards rapid multiplication —— with the progress of agriculture; & the enormous increase in individuals must lead to the occurrence of numerous variations which may be the first time in the [4] development of new species.

At any rate I am able to give you the above mentioned varieties of a particular species; & I may remind you that the group consists of numerous distinct species & genera with a very similar outer[?] and form but exibiting well marked structural differences.

Hoping these facts may be of some service to you[.]

I remain | Very faithfully yours | Frank E. Beddard³ [signature]

A. R. Wallace Esq^e