Miscellaneous. 229 



them, to the exclusion of every individual peculiarity, which passes 

 away with them, and that therefore, while individuals alone have a 

 material existence, species, genera, families, orders, classes, and 

 branches of the animal kingdom exist only as categories of thought in 

 the Supreme Intelligence, but, as such, have as truly an independent 

 existence and are as unvarying as thought itself after it has once been 

 expressed 1 



Returning, after this digression, to the question of individuality 

 among Acalephs, we meet here phaenomena far more complicated than 

 among higher animals. Individuality, as far as it depends upon 

 material isolation, is complete and absolute in all the higher animals, 

 and there maintained by genetic transmission, generation after genera- 

 tion. Individuality, in that sense, exists only in comparatively few 

 of the Radiates. Among Acalephs it is ascertained only for the 

 Ctenophorae and some Discophorae. In others, the individuals born 

 from eggs end by dividing into a number of distinct individuals. In 

 others still, the successive individuals derived from a primary one 

 remain connected to form compound communities. We must there- 

 fore distinguish different kinds and different degrees of individuality, 

 and may call hereditary individuality that kind of independent 

 existence manifested in the successive evolutions of a single egg, pro- 

 ducing a single individual, as is observed in all the higher animals. 

 We may call derivative or consecutive individuality that kind of 

 independence resulting from an individualization of parts of the pro- 

 duct of a single egg. We have derivative individuals among the 

 Nudibranchiate Mollusks, whose eggs produce singly, by a process of 

 complete segmentation, several independent individuals. We observe 

 a similar phenomenon among those Acalephs the young of which 

 (Scyphistoma) ends in producing, by transverse division (Strobila), 

 a number of independent free Medusae (Ephyrae). We have it also 

 among the Hydroids which produce free Medusae. Next, we must 

 distinguish secondary individuality, which is inherent to those indi- 

 viduals arising as buds from other individuals, and remaining con- 

 nected with them. This condition prevails in all the immovable 

 Polyparia and Hydraria : and I say intentionally, in the immovable 

 ones ; for, in the movable communities, such as Renilla, Pennatula, 

 &c, among Polyps, and all the Siphonophorae among Acalephs, we 

 must still further distinguish another kind of individuality, which I 

 know not how to call properly, unless the name of complex individu- 

 ality may be applied to it In complex individuality a new element 

 is introduced, that is not noticeable in the former case. The indi- 

 viduals of the community are not only connected together, but, under 

 given circumstances, they act together as if they were one individual, 

 while at the same time each individual may perform acts of its own. 



As to the specific differences observed among Acalephs, there is as 

 great a diversity between them as between their individuals. In some 

 types of this class the species are very uniform, — all the individuals 

 belonging to one and the same species resembling one another very 

 closely, and exhibiting hardly any difference among themselves, 

 except such as arises from age. This identity of the individuals of 



