ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 177 



male and female. The Cryptoniscid seems to be new ; it is named 

 Enthfilarus trivinctus. It appears that Spondylus gaederopus is an 

 immigrant from the Mediterranean, but the Indian Ocean commensals 

 above noted have found it quite. suitable for their purpose. J. A. T. 



Arthropoda. 

 a. Insecta. 



Oog-enesis in Hymenoptera. — Lancelot T, Hogben {Proc. Roy. 

 Soc, Series B, ] 920, 91, 26S-;»3, 6 pis.). Studies of the oogenesis in 

 Cynips kollari, Rhodites rosse, Synergus rheinhardii, Orthopelma Meolator, 

 Las ills tiara and Formica rufa. All three types of cells (oocytes, follicle, 

 and nurse cells) in the ovary originate from germ cells. The divisions 

 of the oogonia are apparently equipotential, and no .distinction exists 

 between nurse cells and oocytes until after synapsis. After synizesis 

 the haploid number of pachytene threads appear, and in Rhodihs split 

 lengthwise. Daring the growth period there is a diffuse or confused 

 stage. At the termination of the growth period the diploid number of 

 chromosomes reappears, and they pair end to end, so that a temporary 

 separation of the diplotene threads is intercalated between synapsis and 

 the first polar mitosis. This confirms Agar's account of a double 

 syndesis. The restoration of the diploid number by the lengthwise 

 splitting of the haploid pachytene threads permits the inference that 

 the first conjugation is of the type described as parasyndesis. Immedi- 

 ately after this an abortive maturation spindle appears— an interrupted 

 mitotic process. In Rhodites and Cynips there is a reduction of the 

 number of chromosomes in the young oocytes. Secondary nuclei are 

 transitory structures arising from ejected nuclear particles, as Hegner 

 concluded. The oosoma or so-called germ-cell determinant is not of 

 nuclear origin, as believed formerly by Hegner and Silvestri, but arises, 

 as Gatenby affirms, from cytoplasmic granules which are not mito- 

 chondrial. J. A. T. 



Striped Muscle of Wasp.— H. E. Jordan (Amer. Journ. Anat., 

 1920, 27, 1-67, 48 figs.). The comparative histology of the leg and 

 wing niuscle of the wasp, with special reference to the phenomenon of 

 stripe reversal during contraction, and to the genetic relation between 

 contraction bands and intercalated discs. The contraction is associated 

 with a genuine reversal of striations as regards a deeply staining substance 

 of the dark disc of the sarcostyle. This reversal of striatiorjs results in 

 the formation of contraction bands in the contracted fibre. A contrac- 

 tion band is composed essentially of the fused opposite halves of two 

 adjacent dark discs. The striping of the striated muscle fibre results 

 from the segregation of darker and lighter (chromatic and achromatic) 

 substances in alternating dark and light discs. The segregation of 

 anisotropic materials (conditions) in strata alternating with" isotropic 

 levels, and corresponding more or less sharply, under certain conditions, 

 with the dark disc, wotild seem to find its explanation in the relatively 

 more fluid consistency of these dark discs. Anisotropy and the deep- 

 staining character of the dark disc are two essentially distinct phenomena. 



