20 Crust. 
CRUSTACEA. 
to eight weeks to hatch. After sexual maturity, moulting is probably 
not annual. Young lobsters swim at the surface for six weeks. 
Edwards & Bouvier (Bull. Soc. Philom. iii, p. 151) discuss the case 
of a Paguristes found iuhabitiug the left-handed spiral shell of Sinistralia 
maroccana. The example in question was modified to suit its dwelling, 
though it belonged to a genus normally asymmetrical and inhabiting 
right-handed shells. 
For various observations on the habits and morphology of the 
Pagurklce , see Bouvier. 
Isiiikawa has examined twenty males of Gebia major , and found that 
in all of them the hinder part of the testis was ovary-like in appearance, 
and contained egg cells of large size. These are not passed out, but they 
appear to be absorbed at certain seasons of the year. 
Ischikawa describes the occurrence of ova in the testes of Gebia 
major. Zool. Anz. xiv, p. 70. 
Benham (Ann. N. H. (7) vii, p. 256) notices a case of the doubling of 
the female generative pores in Astacus fluviatilis , and of asymmetry of 
the generative pores in Lumbricus herculeus. 
Sense Organs. 
Viallanes (Bull. Soc. Z. Fr. xvi, p. 168) in a preliminary account of 
the minute structure of the eye of Palinurus vulgaris , controverts the 
views of Hickson, which are based, he thinks, on results obtained by 
imperfect methods. 
Szczawinska (Arch. Biol, x, p. 523) has investigated the structure of 
the eyes in certain Crustacea. His results lead him to regard the eyes 
of Branchippus , Gammarus , or Astacus not as compound, but as simple 
eyes with specially differentiated cornea and regularly grouped pigment 
cells. Movements of the pigment cells adapt the eye to varying degrees 
of light. 
vom Rath finds sensory hairs on almost every portion of the Crustacean 
body. The most complicated and important are on the first antennae. 
The function of these dermal sense organs is possibly quite distinct from 
any of our own senses. Zool. Anz. xiv, p. 195. 
Parker (Bull. Mus. C. Z. xxi, p. 45) publishes in considerable detail 
the results of his researches on the compound eyes of Crustacea. He 
recognizes three retinal types. In Isopoda , Branchiopoda i Decapoda , etc., 
the hypodermis simply thickens to form the retina. In Apusidas , PJsthe- 
ridce, and Cladocera , the ectodermal thickening invaginates — the pocket 
closing in the case of the Cladocera , but remaining permanently open in 
the other two forms. In Amphipoda and Copepoda the hypodermal 
thickening separates into the cornea and the retina. The author derives 
a type from which the ommatidia of all Crustacea might be supposed to 
be developed. It bears considerable resemblance to the actual structure 
of the eye of Gammarus. 
Claus (Arb. z. Inst. Wien, lx, pp. 225-264) has an important article on 
the median Crustacean Eye. The subject is dealt with under the follow- 
