416 ZOOLOGY. 



That the characteristics of the organisms in their mature state are 

 those of plants, the universal consensus of botanists indicates; that the 

 embryonic condition at least simulates or even is essentially identical 

 with the amoebiform animals seems to be almost equally certain. Those 

 who knew the entities only in their adult stage would not question their 

 vegetable nature ; those who might be acquainted with them only in 

 their embryonic condition would as little question their animal nature, 

 I)rovided that the protozoans were conceded to be animals. Appar- 

 ently, therefore, they are animals in the earlier period of their existence, 

 and plants in the latter. The question then seems to be whether it 

 shall be admitted that the same organisms may really belong to differ- 

 ent kingdoms at different stages, or whether the pertinence to either 

 shall be decided by the features exemplified in the embryo or the mature. 

 IS'aturalists will recall how strong is the evidence as to affinities fur- 

 nished by development in the animal kingdom, and how by it questions 

 that would be otherwise obscure or insoluble have been completely elu- 

 cidated. Embryological characters are generally most persistent. On 

 the other hand, important changes and modifications may supervene in 

 the early stages of an organism while the adult remain comparatively 

 unchanged. 



Symbiosis of Plants and Animals. 



Several very interesting and remarkable cases of consociation and 

 interdependence between plants and animals have been recorded by Dr. 

 K. Brandt. 



At one time chlorophyll was regarded as a peculiar and distinctive 

 constituent of plants, but it has now long been known as an element 

 occurring also in certain inferior animals. That the chlorophyll had 

 something to do with active vegetation in the animal organism had 

 been suspected, but the exact relations at least were unknown. Carl 

 Semper, it seems, approached the truth when he suggested that the 

 (chlorophyll particles were of the nature of vegetation commensal with 

 the animal. Commensalism, however, fails to express the interrelation 

 between the two. The green particles are truly unicellular i)lants, 

 and they have been discovered under minor modifications in very differ- 

 ent animals — infusoria of various kinds, sponges {Spongilla), acalephs 

 {Hydra), planarians (a fresh-water species). The investigations and 

 experiments conducted by Dr. Brandt and communicated to the Physio- 

 logical Society of Berlin may be said, in brief, to have established the 

 following facts : On the one hand, the algfe elaborate organic matter from 

 inorganic and utilize the waste products of the animal. On the other 

 hand, the animals forsake an independent life so far as capture and in- 

 gestion of food is concerned, and are sufficiently nourished by the plants 

 which have found a home in their bodies. 



Such a relationship cannot properly be said to be one of parasitism 

 or commensalism. The consociation of the two is mutually advan- 

 tageous, and an interdependence is established between them. The pecu- 



