ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 719 



tides. The eggs and the newly hatched larvae contain no yellow-brown 

 cells. If kept in filtered sea- water they remain free from them, but 

 when they are brought into contact with sea-weed from the paradoxa 

 zone, infection is induced. The infecting organism is an alga different 

 from the zooxanthella of Radiolarians ; its free stage is unknown. In 

 the ingested state it is characterised by many ingested chloroplasts, a 

 colourless anterior end, and by the possession of fat-globules in its 

 colourless protoplasm. Once introduced into the body of C. paradoxa 

 the infecting organism multiplies rapidly. The fat-globules of the algal 

 cells are food-reserves. They arise as the result of the photo-synthetic 

 activity of the algal cells. The reserve fat of the algal cells is trans- 

 ferred from these cells to the animal tissues, and serves these tissues as 

 food-material. The ingested yellow-brown algal cells become physio- 

 logically an integral part of the animal, contributing towards its nutrition 

 and incapable of a separate existence. 



The yellow-brown algal cells are indispensable to the animal ; without 

 them it fails to develop. Nevertheless, starved animals digest their 

 algal cells until no trace of them remains. Such animals may be 

 reinfected, and they then begin to grow again. 



Tb.e yellow-brown cells utilise in their constructive metabolism the 

 waste products of the nitrogen-metabolism of the animal. The waste 

 nitrogen of the animal is not excreted, but is stored in the body, prob- 

 ably in the form of urates. Animals deprived of solid food, but kept in 

 the light in filtered sea-water to which uric acid has been added, conserve 

 their yellow-brown cells and maintain their lives longer than do animals 

 not supplied with uric acid. Those supplied with uric acid lay many 

 more eggs than those kept without it, but under conditions otherwise 

 similar. 



The interpretation of the relation between yellow-brown cells and 

 the animal, the author says, depends on the point of view. From that 

 of the animal it is a case of obligate parasitism. From that of the 

 species "infecting organism," it is an insignificant episode, involving the 

 loss of that proportion, probably small, of its members which are ingested. 

 From that of the individual ingested yellow-brown cell it is a solution of 

 the nitrogen problem, a successful method of obtaining large supplies of 

 nitrogen. 



Memory in Convoluta.* — Louis Martin finds evidence of definite 

 correspondence between the behaviour of Convoluta roscoffmsis in arti- 

 ficial conditions and the tidal movements. It seems that this Planarian 

 has a memory for the tides (" pallirintnesia ") but certain conditions 

 bring about amnesia, for instance electric currents. 



Maturation and Cleavage in Paravortex candii.f — Paul Hallez 

 describes in this Rhabdocoel the fertilisation of the ovum, the liberation 

 of two polar bodies, the reduction of the ovum-nucleus to two V-shaped 

 chromosomes, the equatorial plate in the fertilised ovum with its four 

 chromosomes, which soon divide longitudinally, the peculiar lobulated 

 (as if amoeboid) nucleus seen in the blastomeres on to stages of 150-200, 

 and the formation of a multinucleate embryonic plasmodium. 



• Comptes Kendus, cxlvii. (1908) pp. 81-3. t Tom, cit.,pp. 314-16. 



