118 Mr. H.J. Carter on the Organization of Infusoria. 



(tig. 9). Yet it miglit still be observed, that this is no proof of 

 the cyst and diaphane having been originally distinct structures^, 

 — the diaphane may have been re-formed ; in which case I can 

 only refer to what 1 have suggested respecting the origin of the 

 pellicula, and add that what takes place generally in the higher 

 organisms appears to me to be applicable to the lower ones. 

 Certainly we do not find one structure erected by the organism 

 of another in the former, but the production of each structure 

 dependent on the presence of its proper organism ab initio; 

 that is, that the structure docs not appear before it is accom- 

 panied by the fully developed form of the cell or organism which 

 produces it. I do not question that, under the laws of vitality, 

 one organism may occasionally take on the excretory or secreting 

 functions of another, nor that, from a common stock, all organ- 

 isms, in obedience to the same laws, may be adapted to that which 

 is particularly required of them ; but 1 think that when once a 

 being is fully developed, each organ of which it may be com- 

 posed has its peculiar organism, and that organism its peculiar 

 duties, which, except in unusual instances, are the only ones 

 that it is capable of performing. That the diaphane, therefore, 

 should pass into the pellicula, or the pellicula be secreted by the 

 diaphane, seems untenable. 



Related to the diaphane is the transparent intercellular sub- 

 stance of Spongilla, which has a polymorphism equally great 

 with the fully developed cells. This, however, can only be 

 satisfactorily seen when the new sponge is growing out from the 

 seed-like body, at which time it spreads itself over the glass in a 

 transparent film, charged with contracting vesicles of different 

 sizes, and in various degrees of dilatation and contraction. 

 How this substance is produced so early it is difficult to conceive, 

 since it seems to come into existence independently of the de- 

 velopment of the sponge-ovules, which are seen imbedded in it, 

 and there undergoing their transformation into sponge-cells. 

 The spicula too are developed synchronously with the advancing 

 transparent border, from little glairy globules about the size of 

 the largest ovules, which send out a linear process on each side, 

 and thus gradually grow into their ultimate forms. Perhaps 

 the only way of accounting for the early appearance of this in- 

 tercellular substance is to consider that it is a development from 

 some remnants of the original protoplasm, and then that it has 

 the power of secreting a general pellicula, while at the same 

 time it is in part the general diaphane; and perhaps possesses 

 also the power of producing new sponge-cells, as we sec the 

 protoplasm in Vorticella and the roots of Chara producing new 

 buds, viz. independently of the cell-nucleus. 



