MONCECIOUS MOLLUSCA. 345 



the catalogue of systematic naturalists, and complicates the 

 identification of them.* 



The Brachiopoda are all monoecious,-f- every individual 

 of every species being " sufficient to its own felicity." The 

 same is the case apparently with the majority of the ordi- 

 nai'y acephalous bivalves, but the exceptions are yearly in- 

 creasing under the dissections of the comparative anatomist, 

 who has proved several of them to be bisexuous, although the 

 distinction between the male and female does not appear in 

 any external character either of the animal or shell. Some, 

 indeed, of the earlier naturalists discriminate with care be- 

 tween male and female Solencs, but the supposed sexes were 

 in fact either species of different genera, or the siphonal 

 tubes were misinterpreted in their office ; | and as little re- 

 gard would be paid to tlie fisherman, who believes the oyster 

 to be double-sexed, were it not for the particularity of his 

 observation : " The male oyster is black-sick, having a black 

 substance in the fin ; the female white-sick (as they term it), 

 having a milky substance in the fin." § If there is any 

 mistake in the observation it lies in misnaming the sexes, 

 for the latter is the male. Willis and Lister || were of this 

 opinion ; and Deslandes imagined that the females could be 

 distinguished by a delicate edging or border surroimding 

 their bodies, — in which he is wrong. Lister asserts of the 

 fresh-water mussel, that the males and females are in nearly 

 equal proportion ; and he found the ovary of the female full 



* See Steenstrup on the Alternation of Generations, trans, by Busk, 

 p. 38-51 ; Krolin in Ann. des Sc. Nat. (1846), vi. 111.; Agassiz and 

 Gould's Princ. of Zoology, i, 128 ; Forbes and Hanley's Brit. Mol- 

 lusca, i. 47 — 50. Clianiisso's proposition is : That all solitary Salpse 

 produce associated ones or chains ; and on the contrary, that all the 

 associated Salpae are parents of solitary ones, and these again of the asso- 

 ciated, and so on. " Tlie generations of the Salpaj consequently are alter- 

 nately solitary and associated, so that a Salpa mother," to use Clianiisso's 

 familiar expression, " is not like its daughter or its own mother, but resembles 

 its sister, its granddaughter, and its grandmother." — The doctrine has been 

 extended to other classes of the lower animals by Steenstrup, whose attempt 

 to make it embrace the Ascidia and compound Tunicata seems to me a 

 hasty one, I trust in saying so I may not incur the hearty reprehension of 

 Professor E. Forbes. "In vain Chamisso offered the most careful re- 

 searches and minute details of his observations. The heavy-headed in 

 science stigmatised him as a poet and romancer, who carried liis day-dreams 

 into the world of reality, and thus conjured up his wonderful vision of 

 Salpse. jMore than twenty years had to pass away before his staten:ents 

 were fairly treated." — Brit. Moll., i. 48. 



t Owen in Trans. Zool. Soc. Lond., i. 152. 



T Phil. Trans. Ifi84, p. 834. 



i| Sprat's Hist. Roy. Soc, p. 309. 



11 Exerc. Anat. tert. 0. 



