414 Royal Institution of Great Britain. 



spindle-shaped masses. The body then riiptures, aud the small seg- 

 ments escape, each to become a Gregarina, without further change, 

 save the development of a nucleus. Each Gregarina at first appears 

 as a single animal or persona^ which converts itself by segmentation 

 into an aggregation of such beings. There is thus a temporary de- 

 velopment of a compound or colonial state. Similarly the Amcehce 

 (which are low Protozoa, living in stagnant water and infusions, 

 and moving, as do the white corpuscles of our blood, by emitting 

 pseudoitodia, or processes of their protoplasmic substance), when 

 undergoing development, exhibit segmentation or internal division 

 of their substance, and thus exhibit a compound state as a transi- 

 tory feature of their reproductive phases. 



It is noteworthy that in developing from the eggs the embryos of 

 all higher animals exhibit a like process of segmentation or division, 

 as a preliminary phase of their reproduction. There are also forms ■ 

 of Protozoa {Myxodictyum) which are truly "colonial" as adults, 

 and which consist of masses of protoplasm aggregated together to 

 form compound organisms. The Foraminifera are likewise " colo- 

 nial ;" since the shells of these minute Protozoa exhibit, as a rule, 

 a division into chambers, each occupied by a distinct protoplasmic 

 unit, organically connected to its neighbours, from which it was pro- 

 duced by budding. 



The Volvox glohator, formerly known as the " Globe animalcule," 

 but now ascertained to be a free-swimming lower plant, is composed 

 of distinct units, each provided with two cilia, and resembling a 

 Chlamydomonas. Volvox is, in fact, a colony of monads. A Sponge 

 is a compound or "colonial" organism, in that it consists of an 

 aggregation of protoi^lasmic units, some of which resemble Amcehce in 

 nature, whilst others resemble Chlamydomonads, The protoplasmic 

 units of a sponge-colony are, as a rule, united together by a common 

 skeleton they have helped to elaborate. Each sponge grows from an 

 egg, the process of reproduction by " budding" being also represented 

 in the group. Two SponglllcB, or common freshwater sponges, will 

 unite if placed in contact, or may separate spontaneously. The 

 sponge arising from an e^g, like a higher animal, thus exhibits seg- 

 mentation aud segregation of its parts and comes to retain this segre- 

 gate and colonial nature as a permanent feature of the race. 



The Eydrce of the freshwater pools, lead us to a type of animals 

 nearly related to the sponges. Each is a tubular animal which may 

 be artificially divided, aud which throws off gemiiue or buds naturally. 

 Each Hydra-hudi grows into the exact likeness of its parent, and 

 ultimately detaches itself from the parent body. 



The zoophytes are simply Hydrce which have budded, but whose 

 buds remain permanent to form a veritable tree, whose growth is ever 

 increasing, and through whose branches a continual store of nutri- 

 ment is continually circulating. Many zoophytes produce eggs 

 which simply and directly develop into the compound adults by 

 budding. Others develop eggs through the media of jelly-fish or 

 medusoid buds, which break away from the parent tree and live an 

 independent existence in the sea. In some zoophytes there may be 



