242 SUMMARY OF CURRENT RESEARCHES RELATING TO 



they occur, and whether it is possible to infect an animal which has 

 no chlorophyll, by means of a fragment of one which does contain it. 



The morphological investigations were carried out upon Hydra, 

 Spongilla, a fresh-water Planarian, and a variety of Infusoria. The 

 green bodies were isolated by crushing the animals and were then 

 examined with high powers, and it was found that they are not of a 

 uniform colour like the chlorophyll-bodies of plants, but contain 

 hyaline protoplasm. Treatment with haematoxylin always reveals 

 a definite cell-nucleus, and the same is the case if the animals are first 

 killed by • 2 per cent, chromic acid, or 1 per cent, per-osmic acid, then 

 freed from chlorophyll by alcohol, and finally treated with solution 

 of hfematoxylin. These characters prove that what have been 

 described as chlorophyll-corpuscles in animals are really unicellular 

 beings, morphologically independent, which Brandt describes as two 

 new genera of Algae, Zoochlorella, and Zooxanthella, with several 

 species ; the first- named are green, and are met with in animals 

 belonging to the Protozoa, the Sponges, the Hydrozoa and the 

 Turbellaria ; the second are yellow, and are found in some Radiolaria, 

 certain Hydrozoa, and some Actinise. 



Their physiological, as well as their morphological independence 

 can also be established. Thus, if specimens of Zoochlorella are 

 isolated, they do not die, but live for some days, and even weeks, and 

 when exposed to the light are able to develope starch-grains. In- 

 oculation-experiments show besides that the species of Zoochlorella 

 also differ physiologically iiiter se. Green bodies isolated from Spon- 

 gilla and brought into contact with Infusoria devoid of chlorophyll, 

 although in many cases taken in, were unable to persist in the latter 

 animals ; they were either digested or expelled without undergoing 

 any alteration. On the other hand. Infusoria devoid of chlorophyll 

 were successfully inoculated by Zoochlorellce from a dead Hydra 

 viridis. Many Ciliata, absolutely without green corpuscles, absorbed 

 the parasitic forms of the Hydra, and kept them for a long period. 



With regard to the question of the origin of the chlorophyll, 

 Brandt concludes that the animal organisms do not themselves 

 produce it, it being found nowhere but in true plants, so that when 

 met with in animals, it owes its existence to parasites. He describes 

 in the following terms the results to which his experiments have led 

 him : " In making use of the expression ' parasites,' for the yellow 

 and green algge, I have been actuated by the desire of abbreviation, 

 as well as by the fact that morphologically the algae have almost the 

 appearance of parasites on animals. Physiologically, they cannot be 

 regarded as parasites. They cannot be compared with the parasitic 

 fungi, the Tcenice, &c., for these derive their subsistence from their 

 hosts alone, form no nutrient matter themselves, and give out still 

 less, while the species of Zoochlorella and Zooxanthella have the power 

 of producing organic materials (water and carbonic acid) themselves, 

 in the same way as true plants. At first sight, one would expect 

 them not to remove organic matters from their host, but rather to 

 supply them to the latter. What, however, really takes place, and to 

 a very large extent, is shown by the following observations: — 



