Describes anatomy and growth stages of Alcippe in close detail.
Down Farnborough Kent
My dear Sir
I will begin a summary of what I have been able to make out on Alcippe, imagining you feel interest enough to read my scrawl: you must believe, that I express myself positively only for brevity sake.
Mouth: every part peculiar, but strictly on normal type of Lepadidæ: the rudimentary palpi, however, found only in Anelasma. I think your view on the row of hairs on Labrum being Branchial, must be given up; there are thinner but similar hairs on inner opposed tunic of sack, together serving as a fence to prevent anything crawling into sack by the sides of Labrum.
Cirri. The organ you have called palp. or first cirrus, certainly is the
latter, & not much more modified than in Anelasma: the thoracic segment
supporting this cirrus is confluent with mouth & forms the prosoma in normal
manner. The second (N.B this is properly the 3d segment of
archetype crustacean) thoracic segment is large &
obscure; the 3d &
Alimentary canal: œsophagus normal: biliary envelope thick & irregular as in Anelasma: rectum & anus none. I am positive of this latter fact, & it is the most curious point in the anatomy of the genus. Alcippe must always eject (as other cirripedes sometimes do) its excrement from mouth.
Acoustic & olfactory orifices as in Ibla: Eye not discovered. nervous system, hardly examined.
Female organs of generation, all quite normal, as described under the Lepadidæ. The ovigerous fræna are very large & are destitute (as in some species of Pollicipes) of glands: they probably serve as Branchiæ, as well as the universally admitted Branchiæ in sessile cirripedes, of which they are the homologues.
Male organs none, except a rudiment of penis in normal position between & on ventral side of 6th cirrus.
I have forgotten to remark, that the external parts of animal, (capitulum & peduncle) do not essentially differ from same parts in Anelasma, though very peculiar.—
Metamorphoses: in 1st stage, I can add only the minute & lower antennæ. Most fortunately I detected some larvæ, just before their metamorphosis into Alcippe: they are peculiar in having their prehensile antennæ seated almost at very end of quasi-bivalve shell: the abdomen & caudal appendages are peculiar; but they have six pair of natatory thoracic legs & in all other respects resemble the pupæ of Lepadidæ.
Male Alcippe. Almost every female has from 1–3 or more
males attached to her on both sides, externally, near the upper end of the horny shield
or disc on the peduncle, in two little bags, where I have put a cross.
Excavation of burrow. The outer skin or even the whole thickened edge of
orifice into sack with its strong sharp spines is periodically & often moulted:
there is great difference in the state of the star-headed spines on the new
underlying, & the old worn spines on the old membrane: this being the
case, & there being good motive power, in the long, & transverse
& adductor muscles; I do not doubt the excavation is wholly mechanical.
Affinities. I am dreadfully puzzled, & every day change whether to form a family for its reception, as in one point of view it most amply deserves., or to be guided by its varied close affinities to several genera amongst the Lepadidæ & place it in that family. I have never repented in placing Anelasma there; but what to do in this far more puzzling case I cannot yet tell.
I fear my long rambling letter will puzzle & weary you. Accept my very sincere thanks for allowing me to examine this most curious cirripede, & believe me, my dear Sir | Your's very truly | Charles Darwin
- f1 1501.f1CD's detailed description of Alcippe lampas is in Living Cirripedia (1854): 529–63.
- f2 1501.f2For CD's use of homology to interpret cirripede anatomy, see letter to Richard Owen, 17 July , n. 6.
- f3 1501.f3No mention of a rudimentary penis occurs in the description of the generative system of Alcippe in Living Cirripedia (1854): 547–8, 555.
- f4 1501.f4This statement was repeated in Living Cirripedia (1854): 556.
- f5 1501.f5Described in greater detail in Living Cirripedia (1854): 552.
- f6 1501.f6Because Anelasma possessed highly peculiar characters, CD had considered creating a new family or sub-family for its reception. He finally decided that since it had no new or greatly modified organ, it might properly remain among the Lepadidae (see Living Cirripedia (1851): 170).
- f7 1501.f7CD did finally classify Alcippe as a genus in the Lepadidae. See letter to Albany Hancock, 10 February , n. 4, and Living Cirripedia (1854): 526–9 and 554–5.