298 SEA-SIDE STUDIES. 



be added the fact that, according to my observations, sperma- 

 tozoa are rarely met with in the Polypes, whereas ova are 

 extremely abundant. 



All this evidence, however, is as nothing beside that which 

 is furnished in the very remarkable researches on the repro- 

 duction of Aphides made by Professor Huxley, an account of 

 wliich he read to the Linnsean Society, Nov. 5, 1857. Tliat 

 paper not being yet printed, I can only refer to its conclu- 

 sions in as far as they bear on the present topic, and these 

 are — First, that the virgin ^iviparous Aphis, which is said to 

 produce broods of young by " internal gemmation," does 

 really produce them from unfertilised ova : every stage of the 

 development of these ova, and that of the embryos having 

 been carefully made out. Secondly, that the female oviparous 

 Aphis produces her young from ova fertilised by spennatozoa ; 

 but the early stages in the development of these ova are j;re- 

 cisely similar to those of the viviparous Aphis, the differ- 

 ences presenting themselves at a later period, when in the 

 one case the formation of the " mulberry mass " takes place 

 spontaneously, in the other case it is preceded by the union 

 of the spennatozoa with the ova. As the product of both 

 processes is identical — as the Aphis which is seen to issue 

 from an unfertilised ovum is in all respects similar to that 

 which issues from a fertilised ovum — the conclusion is irre- 

 sistible, that Generation is possible from germ-cells only ; and 



system that we have now no evidence of sexuality, whereas in the cryptogamic 

 plants sexual distinctions have been accurately ascertained. It seems to mo, 

 however, that this paradox is more piquant than true, and that the analogous 

 phenomena of Parthenogenesis in animals explain the difficulty, without 

 forcing us to deny the sexuality of the Phanerogamia. 



