134< THE NATURE AND VARIETIES OF 



withstanding the winter cold, all this increase would not 

 avail to the perpetuation of the race, were it not for the 

 provision that, towards the end of summer, a hrood 

 appears capable of complete transformation into perfect 

 insects of both sexes, precisely similar to those of the 

 preceding season, which were the progenitors of the 

 original neuter brood hatched in the spring. 



Now, if we compare this case of alternation with the two 

 previously noticed, we cannot but observe that it is more 

 closely allied to that of Trematoda, than to the modification 

 occurring among the Polypifera, for of all the successive 

 forms in the series the one which bears the sexual organs 

 is undoubtedly that which approximates most to the ideal 

 of the insect type.* So much is admitted by the general 

 phraseology applied to the case, all the sterile forms which 

 proceed being, by common consent, termed larva?. But this, 

 at the same time, suggests the suspicion that the gemmation 

 is referable rather to an early stage of the orthomorphic 

 than to the protomorphic or germinal phase of development. 

 For if the zooids are really equivalent to the larvse of insects 

 generally, their condition corresponds to the embryonic state 

 of other animals for a larva is simply a naked embryo. 

 Now, the larval or embryonic state decidedly belongs, as a 

 whole, rather to the typical than to the germinal stage of 

 development. For the former must be held to include the 

 whole period, from the first commencement of permanent 

 organization till it attains the standard of the adult. The 

 commencement of the permanent organization is a definite 



* It seems not to be the case, however, as is sometimes assumed, that 

 the precursory forms are all without wings, and only the terminal males 

 and females furnished with these organs. It is doubtful if the true 

 females are ever winged, but both neuters and males appear to occur in both 

 guises, the determining conditions being yet unknown. It is much the 

 same with the alternating species in the group to which Chermes belongs. 

 (Huxley, in Annals of Nat. Hist., 3d Ser., II., 214. Leuckart, in do., 

 IV., 321.) 



