BY DAVID G. STEAD. 



755- 



ova--and they are not — fecundation could never take place 

 owing to their inability to extend the pleon. Here the sternal 

 aspect is chiefl}- membranous, though slightly calcified in the fore- 

 part between the bases of the 1st and 2nd pairs of pleopoda. As 

 in the male, this form possesses two hook-like protuberances on 

 the sternal plasti'on, which fasten and keep the pleon in place. 

 In the female these hooks are either rudimentary or are altogether 

 absent. The pleon, in these sterile forms, adheres very tightly to 

 the sternal plastron, so that some little force is required to detach 

 it. Here the female genital oritices, though distinctly visible, are 

 quite rudimentary. They are not perforated, though the oviducts 

 are developed. As in the true female, there are four pairs of 

 pleopoda (Fig. 3, B) all similarly shaped (though in this case they 

 have undergone great modification and are considerably smaller 

 than those of the female) The hairs clothing both exopodite and 

 endopodite are here extremely short — almost rudimentary. Those 

 clothing the former partake of the same plumose, sensory character 

 as those of the same portion of the female, while those of the latter 

 are of the same nature as the ovisrerous hairs of the female. On first 

 examining this kind some two years ago, I was led to think that, as 

 it exhibited a good deal of resemblance to the female, it might be 

 capable of developing into that sex through successive stages at 

 each ecdysis; but in that case I should expect to find some con- 

 necting links between the two; this I had not been able to do, 

 therefore I became of opinion that this form was immutable, but 

 recently, much to my pleasure, by assiduous observation at the 

 Woolloomooloo Fish Market, I have been able to find several 

 specimens which I regard as approaching the female still more 

 closel}'. In these the ovary was a little larger than usual (in fact, 

 only a little smaller than that of the virgin female), the openings 

 of the oviducts also, though still extremely small (too small for 

 the passage of ova) were far more in evidence, the hairs on the 

 pleopoda were considerably lengthened, and lastly the pleon was 

 fringed with extremely short hairs. The pleon itself had not 

 undergone much change, but this is not of ^ery great moment. 

 Incidentally, I might mention that one of the first things that 



