APPENDIX V 311 



finds, numbering 10,000 individuals, did not contain a single 

 male. I have found no record of a male L. glacialis, and 

 none of the twenty odd specimens of the Spitzbergen 

 variety I have as yet examined have been males. It is 

 probable that throughout the whole genus self-fertilisation 

 is taking the place of cross-fertilisation, but that some 

 species have gone further than others in dispensing with 

 males. Two species, for instance, L. couesii, Packard, and 

 L. macrurus, Lilljeborg, are reported to have more males 

 than " females " (?), but the finds in these cases seem hardly 

 large enough to allow us to judge ; it may have been purely 

 accidental that more males than " females " were caught. 



The males of the Apodidae, with the doubtful exception 

 of L. productus, seem to be smaller than the hermaphrodites, 

 otherwise there is no very pronounced sexual dimorphism, 

 as there is among the Cirripedia. We are perhaps justified 

 in concluding from this that the hermaphroditism of the 

 Cirripedia is of much older date than that of the Apodidae. 

 No comparison is here, however, possible, since the two 

 have nothing further in common beyond the fact that they 

 are both hermaphrodite, and that this hermaphroditism is in 

 both cases an adaptation against extermination through too 

 wide dispersion of the individuals. 



B. ON THE FORMATION OF THE EGGS. 



The regular formation of the eggs out of four cells, of 

 which three are nutritive and one the definitive egg-cell, 

 gives opportunity for many interesting observations. The 

 general method of growth is shown in Fig. 33, p. 144, 

 where we see the egg in different stages. 



The originally round group of cells as a rule soon 

 becomes oval, in consequence of the more active growth 



