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NOTE ON THE ABNORMAL DEVELOPMENT OF THE GENITAL 
OEGANS OF J ASUS LALANDII (Milne Edw.). 
By W. von Bonde, B.A. 
(With two Text-figs.) 
The peculiar phenomenon here recorded was noticed on a male Crawfish 
found among the specimens procured for laboratory purposes by the South 
African College Zoological Department. 
An examination of the external features of the animal showed the 
presence of the usual pair of genital apertures, which in the male are 
situated on the fifth pair of pereiopods or walking legs, but in addition to 
these two normally developed (n.y.a.) openings, there was observed a third 
abnorinall'y developed aperture (ahjj.a.) which occurred on the fourth 
pereiopod on the right side only. 
A closer examination of this interesting abnormality revealed the fact 
that the last or fifth walking leg of the right side, on the basal segment of 
which was situated one of the normal apertures, took its origin from a point 
comparatively far in under the sternal elements. The latter thus formed a 
hard projecting edge over part of the basal segment of the limb, with the 
result that the genital aperture (n.g.a.), which is noi-mally developed close 
to the articulating point of limb and body, became partially obscured, 
The endopodite portions of this particular limb, it may be mentioned, 
were wanting when the animal was discovered, but there is little doubt that 
the missing parts had only recently been lost (probably during fishing 
operations), as the muscle tissues showing at the break were perfectly fresh, 
presenting a white and soft appearance as contrasted with the hardened, 
brown surface of the same structures when exposed for any length of time. 
The abnormal opening, it may also be mentioned, was developed to per- 
fection as far as the appearance with regard to shape, size, and position is 
concerned. 
A dissection of the specimen was also performed in order to determine 
the exact relation between this external appearance and the associated 
internal genital organs. The peculiar development showed the following 
interesting facts : 
The testes of Jasus lalandii normally appear as bilaterally, symmetrically 
disposed organs, each composed of two distinct lobes. The anterior ones, 
situated laterally to the digestive tract and passing forwards into the head 
region, are united above the intestine directly behind the mesenteron by a 
