102 MORPHOLOGICAL DEVELOPMENT. 



Thus even in the higher Anmclosa, the much greater conso. 

 lidation and much greater heterogeneity do not obliterate the 

 evidence of the fact, that the organism is an aggregate of 

 the third order. Beyond all question it is divisible into a 

 number of proximate units, each of which has essentially the 

 same structure as its neighbours, and each of which is an 

 aggregate of the second order, in so far as it is an organized 

 combination of those aggregates of the first order which we 

 call morphological units or cells. And that these segments 

 or somites, which make up an annulose animal, were origin- 

 ally aggregates of the second order having independent in- 

 dividualities, is an hypothesis which gathers further support 

 from the contrast between the higher and the lower articu- 

 late types, as well as from the contrast between the Articu- 

 lata in general and the inferior Annulosa. For if that 

 masking of the individualities of the segments which we find 

 distinguishes the higher forms from the lower, has been going 

 on from the beginning, as we may fairly assume ; it is to be 

 inferred that the individualities of the segments in the lower 

 forms, were originally more marked than they now are. 

 Reversing those processes of change by which the most 

 developed Annulosa have arisen from the least developed ; 

 and applying in thought this reversed process to the least 

 developed, as they were described in the last Chapter ; we 

 are brought to the conception of attached segments that are 

 completely alike, and have their individualities in no ap- 

 preciable degree subordinated to that of the chain they com- 

 pose. From which there is but a step to the conception of 

 gemmiparously-produced individuals which severally part 

 one from another as soon as they are formed. 



§ 209. "We must now return to a point whence we di- 

 verged some time ago. As before explained under the head 

 of Classification, organisms do not admit of uni-serial ar- 

 rangement, either in general or in detail ; but everywhere 

 form groups within groups. Hence, having traced tha 



