308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the alimentary canal. It is the organ described by other authors in 

 adult Pediculi, and peculiar to them, as an abdominal gland of unknown 

 function. 



5. Arachnida. 



Development of Scorpions.* — I. Poljansky gives some notes on 

 the yolk and embryonal envelopes, including the relation to the mother 

 during intra-uterine life, in Scorpio indicus. At first, while in the uterus, 

 the embryos are semi-transparent, and do not appear to have so much 

 yolk as other scorpions. The embryo after a certain time becomes 

 detached from the mother through the gradual separation of the inner 

 layer of the uterus from its attachment. The passage of the nutritive 

 material continues by osmosis, a process which is aided by the presence 

 of folds upon the dorsal and lateral regions of the body, which increase 

 the absorptive surface. 



Two new forms of Trombidium parasitic in Man.f — F. Heim and 

 A. Oudemans have found in several consecutive summers three specifi- 

 cally distinct larval forms of Trombidium parasitic in man. One of 

 these larval forms is referable to T. gymnopterorum ; the others to new 

 species, T. poriceps and T. striaticpps. Their salient characters are de- 

 scribed. The new species have been found also in various mammals, 

 birds and insects. The three species may occur together in the human 

 skin. All the observations relate to the same locality in France (Bure- 

 la-Forge, Meurthe-et-Morelle) . 



Comparative Anatomy of Mites.| — Thor completes an elaborate 

 account of the comparative anatomy of prostigmatic Acarina, in which 

 he deals with the skin, the endosternite, the connective tissue, the 

 leucocytes, the respiration, the digestive apparatus, the cutaneous and 

 salivary glands, the excretory organs, the nervous system, the sensory 

 organs, and the gonads. 



e. Crustacea. 



Proportion of Sexes in Shore-Crab.§ — R. C. Punnett has studied 

 in reference to Mendel's law the proportion of the sexes in Carcinus 

 manias. From his data, which relate to 3583 crabs — 80 '6 males to 100 

 females — Punnett thinks it may be fairly concluded that (1) during the 

 early stages of growth the proportion of the sexes is equal, and that 

 (2) the approach of sexual activity is accompanied by changes of habit 

 and disposition which, by exposing the males to greater risks, lead to 

 an increased mortality during later stages of growth in this sex, as 

 compared with the females. 



If we assume that the death rate in the larval and early post-larval 

 stages is equal for the two sexes, then the former of the above two 

 conclusions is in accordance with the view that Mendel's law applies to 

 sex heredity in the crab. The second conclusion suggests the danger 

 of drawing any conclusion as to the relative numbers in which the 



* Zool. Anzeig., xxvii. (1904) No. 2, pp. 49-58. 



t Comptes Rendus, cxxxviii. (1904) pp. 704-G (9 figs.). 



X Ann. Sci. Nat. (Zool.), xix. (1904) pp. 1-190 (9 pis. and 59 figs.). 



§ Proo. Cambridge Phil. Soc, xii. (1904) pp. 293-0. 



