18 [322] 



DARWIN AND HUMBOLDT. 



minute parasites, on the margins of 

 both scuta, close to the umbones. I 

 carelessly dissected one or two speci- 

 mens, and concluded that they be- 

 longed to some new class or order 

 among the Articulata, but did not 

 at the time even conjecture that they 

 were Cirripedes. Many months af- 

 terward, when I had seen in Ibla 

 that an hermaphrodite could have a 

 complemental male, I remembered 

 that I had been surprised at the small 

 size of the vesiculae seminales in the 

 hermaphrodite S. vulgare, so that I 

 resolved to look with care at these 

 parasites; on doing so I now dis- 

 covered that they were Cirripedes, 

 for I found that they adhered by ce- 

 ment, and were furnished with pre- 

 hensile antenna?, which latter, I ob- 

 served with astonishment, agreed in 

 every minute character, and in size, 

 with those of S. vulgare. I also found 

 that these parasites were destitute of 

 a mouth and stomach ; that con- 

 sequently they were short-lived but 

 that they reached maturity ; and that 

 all were males. Subsequently five other 

 species of the genus Scalpellum were 

 found to present more or lsss closely- 

 analogous phenomena. These facts, 

 together with those given under Ibla 

 (and had it not been for this latter 

 genus, I never probably should have 

 struck on the right line in my investi- 

 gation), appear sufficient to justify 

 me in provisionally considering the 

 truly wonderful parasites of the seve- 

 ral species of Scalpellum, as Males and 

 Complemental Males." (vol. i. pp. 

 292-3). 



The remarkable phenomena of 

 sexuality in these animals is summed 

 up thus : 



" The simple fact of the diversity in 

 the sexual relations displayed within 

 the limits of the genera Ibla and Scal- 

 pellum, appears to me eminently curi- 

 ous. We have (1) a female, with a 

 male (or rarely two) permanently 

 attached to her, protected by her, and 

 nourished by any minute animals 

 which may enter her sac ; (2) a female, 

 with successive pairs of short-lived 

 males, destitute of mouth and stom- 



ach, inhabiting the pouches formed 

 on the under sides of her two valves; 

 (3) an hermaphrodite, with from one 

 or two, up to five or six, similar 

 short-lived males without mouth or 

 stomach, attached to one particular 

 spot on each side of the orifice of the ca- 

 pitulum ; and (4) hermaphrodites, with 

 occasionally one, two, or three males, 

 capable of seizing and devouring their 

 prey in the ordinary Cirripedal meth- 

 od, attached to two parts of the 

 capitulum, in both cases being pro- 

 tected by the closing of the scuta." 



With reference to these Comple- 

 mental Males (so-called "to show that 

 they do not pair with a female, but with 

 a bisexual individual.") Mr. Darwin 

 further observes : "Nothing strictly 

 analogous is known in the animal 

 kingdom ; but amongst plants, in the 

 Linnean class Polygamia, closely 

 similar instances abound ; " and also 

 that "in the series of facts now given 

 we have one curious illustration more 

 to the many already known, how 

 gradually nature changes from one 

 condition to the other, in this case 

 from bisexuality to unisexuality." 

 (ii. 29). 



Lastly, to give only one other quo- 

 tation from this work, he writes : 



" As I am summing up the singu- 

 larity of the phenomena here present- 

 ed, I will allude to the marvelous 

 assemblage of beings seen by me 

 within the sac of an Ibla quadrival- 

 vis, namely, an old and young male, 

 both minute, worm-like, destitute of a 

 capitulum, with a great mouth and 

 rudimentary thorax and limbs, attach- 

 ed to each other and to the hermaph- 

 rodite, which latter is utterly dif- 

 ferent in appearance and structure ; 

 secondly, the four or five free, boat- 

 shaped larvae, with their curious pre- 

 hensile antennas, two great compound 

 eyes, no mouth, and six natatory 

 legs ; and lastly, several hundreds of 

 the larvae, in their first stage of de- 

 velopment, globular, with hora-shaped 

 projections on their carapaces, minute 

 j single eyes, filiform antennae, pro- 

 I bosciform mouths, and only three 

 ! pairs of natatory legs. What diverse 



