322 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of a large one. The large primary pygidium was probably, as Spencer 

 suggested, of use as a caudal fin in swimming. Perhaps the group had 

 a pelagic rather than a benthonic origin. J. A. T. 



e. Crustacea. 



Life-history of Cape Crawfish. — J. D. F. Gilchrist {Joum. 

 Linn. Soc. ZooL, 1920, 34, 180-201, 2 pis., 13 figs.). The embryonic 

 development of Jasus lalandu remains unknown, but the naupliosoma 

 stage and the phyllosoma have been observed. The transition from 

 the phyllosoma to the puerulus is not known, but the pueruli have 

 been followed to the post-puerular stage. The red spots on the 

 underside of the puerulus disappear and all the upper parts become 

 coloured ; the spines of the carapace, definite in number in the 

 puerulus, become much more numerous ; there are changes in anten- 

 nules, mandibles and some other appendages ; the exopodites of the 

 pereiopods disappear ; the cervical groove is well marked ; the telson 

 has additional spines ; and so on. The post-puerulus differs from 

 succeeding stages in having the cuticle uncalcified, in having the 

 incisor part of the mandible provided with denticles on the margin of 

 its thick cuticle, in showing no sex differentiation in the pleopods, 

 and in the third maxillipedes being separate at their bases. J. A. T. 



Species of Asellus. — E. G. Racovitza {Arch. Zool. Exper.^ 1919, 

 58, Notes et Revue, 31-43, 12 figs.). It appears that Asellus aqKcitkus 

 auct. is a taxonomic error which has lasted for nearly two centuries. 

 Under this name there are ranked a medley of different forms, of 

 diverse origin and taxonomic value, but not forming one species. 

 The author differentiates a northern species Asellus aquaticus Linne and 

 an older species A. meridianus of more southern distribution. J. A. T. 



Study of Asellus. — E. G. Racovitza {Arch. Zool. Exper., 1919, 

 58, Notes et Revue, 49-77, 38 figs.). A minute discussion of Asellus 

 coxalis sp. n. (Syrian), A. coxalis peyerimhoffi subsp. n. (Algerian), and 

 A. ianyidensis (France), which in respect to several important structures 

 form a very definite orthogenetic series. The origin of the stock may 

 be looked for in Asia Minor, whence it has spread along the southern 

 shores of the Mediterranean. Attention is also directed to the sex 

 dimorphism and to the abundance of a large commensal protozoon, 

 Stylocometes cUgitatus CI. and L., on the endopodites of the pleopods. 



J. A. T. 



Studies on Asellidae. — E. G. Racovitza (Arch. Zool. Exper., 1920, 

 58, Notes et Revue, 79-115, 33 figs.). A detailed discussion of the 

 first and second pleopods in Asellidie, which have come to be associated 

 with reproduction and have undergone reductions and transformations. 

 In the male the first pleopod is reduced to two undivided joints, a 

 sympodite and an exopodite ; it is absent in the female. In the male 

 the second pleopod shows an undivided sympodite, a slightly modified 



