16 



MORPHOLOGICAL DEVELOPMENT. 



finiteness, as well as increasing extent. In the yeast-plant, 

 Fig. 7, we have cells which may exist singly, or joined into 

 groups of several ; and which have their shapes scarcely at 

 all modified by their connexion. Among the Desmidiacece, it 

 happens in many cases, that the two individuals produced by 

 division of a parent-individual, part as soon as they are fully 

 formed ; but in other cases, instead of parting they compose 

 a group of two. Allied kinds show us how, by subsequent 

 fissions of the adherent individuals and their progeny, there 

 result longer groups ; and in some species, a continuous thread 

 of them is thus produced. Figs. 8, 9, 10, 11, exhibit these 



several stages. Instead of linear aggregation, some of the 

 Desmidiacece illustrate central aggregation ; as shown in 

 Figs. 12, 13, 14, 15. Other instances of central aggrega 

 tion are furnished by such protophytes as the Goniurn pector- 

 ale, Fig. 16 (a being the front view, and b the edge view), 

 and the Sarcina veutriculi, Fig. 17. Further, we have that 

 spherical mode of aggregation of which the Vohox globator 

 furnishes a familiar instance. 



Thus far, however, the individuality of the secondary ag 

 gregate is feebly pronounced : not simply in the sense that 

 it is small ; but also in the sense that the individualities of the 

 primary aggregates are very little subordinated. But on 

 seeking further, we find transitions towards forms in which 

 the compound individuality is more dominant, while the sim 

 ple individualities are more obscured. Obscuration 

 of one kind, accompanies mere increase of size in the second- 

 arv Aggregate : in proportion to the greater number of the 



