OF THE SALP.E. 43 



tiles at one time bring forth eggs, whilst at another, the 

 shell of the egg is ruptured at an earlier period, and living 

 young are produced, &c. ; but notwithstanding this, the 

 young from the eggs and those which are born alive, en- 

 tirely correspond in theh" organization. In the humble- 

 bee and wasp, we also know, that larvae are produced 

 from the fu-st deposited eggs, which only attain a definite 

 and lower degree of development, whilst the larvae from 

 the ova which are deposited at a later period by the same 

 females, attain another and a higher stage ; but so far as 

 we are at present acquainted with their nature the larvae 

 from all the ova, are indebted for the degree of develop- 

 ment which they respectively attain, whether higher or 

 lower, only to the adventitious and extraneous care which 

 is devoted to them; and I believe it would be very difficult 

 to find in the whole of nature, anything analogous to that 

 which is supposed by Eschricht.* Inasmuch as that in 

 an organization in other respects similar, we must always 

 presume that organization or state of development to be 

 the higher and more complete which exhibits the greatest 

 degree of independence, and the existence of which is 

 connected in the least degree with the coexistence of 

 another similar organization, and as in this respect a free 

 swimming form must be considered as more highly de- 



* This first objection, which is not exactly the same with the only one 

 made by Professor Eschricht to his own theory, namely that the embryos 

 never resemble their mother, but that the young of a solitary salpa, in their 

 form, iuvariably resemble the associated, whilst those of an associated salpa 

 always assume the solitary form, loses none of its weight from the assumption 

 of Professor Eschricht, that the reason of the difference of form which exists 

 between the associated and the solitary salpa-embryos lies especially iu their 

 connexion. Eor the circumstance that the individuals of the one generation 

 of embiyos are connected by peculiarly developed organs, whilst, on the con- 

 trary, the other generation wants those organs and consists of unassociated 

 embiyos, is much more essential than a slight difference between the two 

 generations, iu the outlines of their external figure, and in the relative extent 

 of certaiu organs, which besides are common to them both. Stul it by no 

 means follows, that the reason of the difference iu form between the asso- 

 ciated and solitary salp(S should exist simply iu their connexion ; for there is 

 some common, iutemal, fimdamental principle concerned iu the necessary 

 occurrence of such an interconnexion, and of the organization conducive to 

 it, which it would be vain to attempt to demonstrate with our present amoiuit 

 of knowledge. 



