594 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and least dense plasmic structure seem to be most influenced, but mucb 

 also depends on the envelopes and skeleton. 



Lake Plankton.* — Dr. Otto Zacharias records the occurrence of tbe 

 Infusorian Trichodina pediculus in great numbers in a plankton gathering 

 from Lake Hertba. Tbe gathering consisted of the Infusorian and of a 

 few Crustacea and Eotifers. The point of interest is that Trichodina 

 usually occurs as a parasite on Planarians, Hydra, and young fishes; 

 but this observation, together with one by Dr. A. Seligo on a lake near 

 Marienburg, shows that it does also occur as a free-swimming form. A 

 somewhat analogous fact is the occasional occurrence of the Rotifer 

 Actinurus neptunius Ehrb. as a plankton form, while it is usually found 

 in mud or in the plant zone near the shore. 



Plankton of Gulf of Naples.f — Bruno Schroder publishes a paper 

 on the phytoplaukton of the Gulf of Naples, which not only includes 

 such members of the Protista as the Peridiuiaceaj, but also to some 

 extent is concerned with the plankton as a whole. He finds that a line 

 drawn approximately from Cap Miseno to Castellamare divides the Gulf 

 into two regions so far as the plankton is concerned ; but if tbe scirocco 

 blow persistently the distinction becomes obliterated. In the inner 

 region, owing apparently both to the temperature and to tbe condition of 

 the water as influenced by surface drainage, Copepoda swarm in enormous 

 numbers, and Peridiniea3 and Diatoms are relatively less abundant. In 

 the outer region the Copepods are less abundant, and Sagittse, Radiolaria, 

 Peridinieae, and Diatoms occur freely. As regards the affinities of the 

 Neapolitan plankton, the author's results confirm those of Schiitt 

 that not onJy do the species correspond to those of the warmer parts 

 of the North Atlantic, but there is also strong resemblance in regard to 

 the range ol variation and tbe paucity of individuals, as contrasted with 

 the great number of species. The occurrence of similar variations in the 

 North Atlantic and the Gulf of Naples is especially striking in regard 

 to the species of Ceratium, notably the very variable G. tripos. The 

 reason is probably to be sought in the warm superficial current which 

 enters the Mediterranean through the Straits of Gibraltar, and is pro- 

 duced by a branch of the Gulf Stream. 



Malarial Parasites.^— Dr. J. W. W. Stephens and Mr. S. E. Chris- 

 tophers find that tbe parasite of malaria may occur in fresh blood in one 

 of two forms : it may be unpigmented throughout, or it may have one or 

 several pigment spots from the earliest stages onwards. By the use of 

 gentian-violet or hamiatiu (modified Thin's formula) they succeeded in 

 staining blood-films so that leucocytes, erythrocytes, and parasites showed 

 up clearly. The very young parasites consist of a staining ring (chro- 

 matic substance) surrounding a central achromatic body. Later there 

 are in addition a chromatic body on the periphery of the ring, and also 

 one or more minute chromatic bodies. As the parasite grows the chro- 

 matic substance increases, usually unilaterally, and a differentiation 

 takes place in tbe expanded region, whose significance is not understood, 

 and which is not always identical in nature. When full-grown the 



• Biol. Centralbl., xx. (1900) p. 463. 

 t MT. Zool. Stat. Neapel, xiv. (1900) pp. 1-38 (1 pi.). 



t Roy. Soc. Lond. Reports to Malaria Committee, 1899-1900, pp. 12-42 (10 charts). 

 Cf. ante, p. 578. 



