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Darwin Correspondence Project

From B. P. Brent   15 June 1861

Dallington | nr. Robertsbridge | Sussex.

June 15th. 1861

Dear Sir,

Being in conversation the other day with my Father respecting his crossing the Cacti, he said he found them quite fertile and averaged three seeds to a fruit, but the seeds varied very much in the period of germination, he had crossed some several times—1 the following I took from his dictation as I thought it might interest you

〈Respe〉cting the fertility of hybrids:


The Hybrid Cactus, Jenkensoni, reproduced with one parent viz Epiphyllum Speciosum;—


The Hybrid Cereus Cactus, Mallisoni, reproduced, with Epiphyllum Ackermani;


Cactus Jenkensoni, itself a hybrid of Epiphyllum Speciosum, and Cereus Speciosissimus—reproduced with the Hybrid Cereus Mallisoni, which was produced between Cereus Speciosissimus and Cereus Flagelliformis— or it may be stated thus.

Epiphyllum Speciosum

and produced Jenkensoni.

Cereus Speciosissimus reproduced a compound


Cereus Speciosissimus

and produced Mallisoni

Cereus Flagelliformis

Unfortunately my Father has no memoranda of his crosses nor did he have any of his productions named. but I think you may rely on the the truth of the abo〈ve〉

〈A〉 second Sow Guinea pig went 〈to〉 boar on the 13th. inst. I have 〈p〉ut her in a hutch by the fire and shall keep her as warm as I can, the one that went on May 25th. is out of doors in a north aspect and as cold as I can place her, so I hope to see if temperature has any effect.2

Miss Watts in a recent letter wished me to inform you she found the Crested fowls stupid but she puts in a word for her favourite Brahmas— I enclose that part of her letter.3

I am | Dear Sir | Your’s sincerly | B P Brent

To C Darwin Esqr.

CD annotations

0.3 Dear … times— 1.4] crossed red crayon
4.1 〈A〉 second … effect. 4.4] crossed red crayon
5.1 Miss … Brent 6.1] crossed ink


CD was particularly interested in cactus hybrids as they indicated that even species with marked external differences could produce fertile progeny (see Natural selection, pp. 412–13). For an earlier source of information on this point, see Correspondence vol. 6, letter to J. D. Hooker, 30 September [1857], and letter from Thomas Glover, 26 October 1857.
CD wanted to know how changes in external conditions affected the fertility of organisms and their tendency to vary; aspects of the topic are discussed in several of the chapters of Variation. In Variation, 2: 161, CD stated that many domesticated animals ‘can bear with undiminished fertility the most unnatural conditions’. No mention, however, was made of the results of Brent’s breeding experiments.
The enclosure from Elizabeth Watts has not been located. According to entries in the Catalogue of Down specimens (Down House MS), CD had received specimens of fowls from Watts via Brent. She is mentioned in Variation 1: 228 n. 2 as the author of the best account of sultans, a Turkish breed of crested fowls. The reference may be to the section on sultans in Watt’s revised edition of William Charles Linnaeus Martin’s The poultry yard (Martin 1855, pp. 78–80). CD was investigating whether the remarkable bony protuberances of various crested breeds of fowl in any way affected the individual’s intelligence (see Variation 1: 262–6).


On his father’s crossing experiments with cacti, in which hybrids were found quite fertile.

On his breeding of guinea-pigs.

Sends Miss E. Watts’s message about crested fowls and Brahmas.

Letter details

Letter no.
Bernard Peirce Brent
Charles Robert Darwin
Sent from
Dallington, Sussex
Source of text
DAR 160.2: 300
Physical description
4pp damaged †

Please cite as

Darwin Correspondence Project, “Letter no. 3184,” accessed on 20 January 2018,

Also published in The Correspondence of Charles Darwin, vol. 9