ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 307 



Effect of Radium on Fertilization Membrane of Nereis. — Alfred 

 C. Redfield and Elizabeth M. Bright {Amer. Journ. Physiol., 1918, 

 45, 374-87) find that the fertilization membrane of the Q^g of Nereis 

 limhata becomes abnormally thick if the Qgg is exposed to radiations 

 from radium prior to fertilization. The change leading to the condition 

 is irreversible. The physiological effect is not proportional to the 

 product of intensity and time. The time factor is relatively more 

 important than the intensity factor. J. A. T. 



Branchiobdellids from Michigan Crawfishes. — Max M. Ellis 

 {Trans. Amer. Micr. Soc, 1918, 37, 4:9-.51) defines and distinguishes 

 Xironodrilus formosus Ellis in ed., Camharincola vitrea Elhs in ed.^ 

 C. philadelphica (Leidy), and Pterodrilus durhini Ellis in ed. from 

 numerous crawfish hosts. J. A. T. 



Nematlielinintlies . 



Filter-bed Nematodes. — N. A. Cobb {^Nemntologij, Baltimore, 1918, 

 189-212, 9 figs.) finds that towards the end of a period of use the 

 number of Nematodes in the topmost three inches of a filter-bed often 

 amount to hundreds of millions per acre, and sometimes exceeds a 

 thousand millions. About thirty species were found. The commonest 

 are carnivorous. Their soluble excretions may give flavour to water. 

 A description is given of the process of discharging the secretion from 

 the caudal glands. It is pointed out that species of Nematodes regarded 

 as parthenogenetic may turn out, as in the case of Plectus, to have 

 minute functional spermatozoa. Some hermaphrodite forms begin by 

 producing spermatozoa which are stored till the ova are produced. The 

 reproductive phenomena are discussed and new terms are proposed. A 

 number of new genera and species are described and figured. J. A. T. 



Development of Ascaris lumbricoides and A. mystax in Mouse. — 

 F. H. Stewart {Parasitology, 1918, 10, 189-96, 1 pi.) has continued 

 his study of the migration of A. lumhricoides in the mouse, and has 

 followed the course of the parasites from the ninth to the fifteenth day, 

 during which period many make their way down the intestine. The 

 structure of the young stages is described. Cultures of A. mystax in a 

 damp atmosphere showed three-cell stages on the first day, advanced 

 segmentation on the second, curved vermicules on the fourth and fifth, 

 plump vermicules on the seventh, and so on. Ripe eggs were given to 

 mice, and active larvse were found in the liver between the first and third 

 days after infection. J. A. T. 



Life-history of Ascaris lumbricoides. — F. H. Stewart {Para- 

 sitology, 1918, 10, 197-205) finds that ripe eggs of A. lumbricoides or 

 A. suilla hatch in the intestine of their definitive hosts, man or the pig, 

 and also in the rat and mouse, and develop in the body of man and of 

 these animals in an identical manner up to the 2 mm. larva in the 

 trachea. Further, that in the mouse the larvae then pass through the 

 ahmentary canal unharmed and are evacuated in the faeces. It may be, 

 however, that the normal development of either species is in one host 



