My dear Sir

The sexual difference in Mallotus has been known for a long time, as you will see on looking over the references in my Catalogue Vol. VI. p. 170, but I do believe I never thought of this fish, when giving you instances of this kind some years ago. The fish is called “Capelin”, & belongs to the family of Salmonidæ, order Physostomi.¹

The genus Monacanthus belongs to the family Balistidæ or “Trigger-fishes”, order Plectognathi widely different from the former.²

What you say about the use of these brushes in mature males, astonishes me: and I must look up the article in the American Naturalist.³ It must be very strong evidence, indeed, from a reliable source, to remove any doubts I still entertain about it. There is nothing known of the propagation of Monacanthus. Excrescences homologous to the brush of Monacanthus, but in the form of spines or tubercles are found in Acanthurus, Naseus etc, which belong to the order Acanthopterygii.⁴ But in these genera they are equally developed in both sexes, but less so in the young than in the adult.

Who is your authority for the remarkable observation that 2 males attend 1 female among Cyprinidæ? I have watched them spawning over & over again, and never observed anything of the kind: they generally spawn in shoals, where all is confusion.⁵ I have seen single female Barbels attended by 2, 3, 4 & probably more males.⁶

Yours very truly | A Günther

I am, at present, deep in the Cephalopods, & had under my hand the very specimens you watched in St Jago, & the habits of which you describe in the “Journal”. The species is Octopus rugosus.⁷

I have come across a specimen in which the entire oral apparatus is absent; & there is no trace of an injury. The central opening leads direct into the stomach. This defective nutrition led to a very anomalous development of the various parts: arms of nearly normal size, suckers very small & retracted, body reduced to a small appendage.