ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 125 



deposited. No worm was ever observed above the surface of the sand 

 during the day. 



Snow-field and Glacier Olig-ochaeta.*— Paul S. Welch describes 

 from Mt. Rainer, Washington, 2Ies6nchytrseus gelidus sp. n., from 

 elevations of 2700-5000 feet, and M. solifugus rainierensis var. n. 

 from an elevation of 7500 feet. The description pays special attention 

 to the minute structure of the reproductive organs. It is probable that 

 the food consists in part of minute snow Algae. The mature forms of 

 both species are dark in colour, as are some other glacier animals. The 

 pigmentation is probably in some way adaptive. 



Nematohelminthes. 



Sclerostome Parasites of Horse. f — Charles L. Boulenger describes 

 Triodontophorus teiiuicolJis sp. n., T. hrevicauda sp. n., T. intermedius 

 Sweet, and (Esoiplunjodontus robustiis Giles, from English horses. 

 Sclerostomes are responsible for a considerable amount of damage to 

 horses, and it is very important that reliable and full information 

 should be available in regard to the different forms and their life- 

 histories. 



Germ-cells in Ascaris incurva.l — H. B. Goodrich has made a 

 study of the development of the germ- cells in Ascaris incurva, a form 

 which seems more suitable for investigation in the early stages than the 

 ])etter-known A. megalocephala. There is in tI. incurva a sex-chromo- 

 some complex, consisting of eight a;-chromosomes and one ^-chromosome, 

 which is mated by a detinite component of the :c-group. The elements 

 of the ii'-group appear to be mutually independent except during the 

 reduction division. The a;-chromosomes are carried to one pole in the 

 reduction division on account of their attachment to one member of a 

 bivalent chromosome unit, consisting of the y-chromosome and its 

 mate among the .c-components ; otherwise these elements are equally 

 affected by the opposing forces acting during the first phase of mitotic 

 division. The heterotypic mitosis may be divided into two phases ; 

 one characterized by action of equal and opposite forces from the 

 spindle pole, the other by an apparent cessation of the forces and 

 movements probably due to cytoplasmic currents. Measurement of 

 volumes of nuclei of spermatozoa gives a bimodal curve, and the ratio 

 between the volumes of nuclei of the modal classes is closely proportioned 

 to the ratio between the numbers of chromosomes contributed respec- 

 tively to the male-producing and female-producing spermatozoa. The 

 ^-chromatin is indistinguishable from other chromatin during the 

 growth stages. The growth stages present a seriation comparable with 

 that of other forms, and therefore ylscms need not be considered 



* Trans. Amer. Micr. Soc, xxxv. (1916) pp. 85-124 (4 pis.). 



+ Parasitology, viii. (1916) pp. 420-39 (1 pi. and 7 figs.). 



X Journ. Exper. Zool., xxi. (1916) pp. 61-99 (3 pis. and 11 figs.). 



