756 AUSTRALIAN CRUSTACEAN FAUNA, 



attracted my attention (prior to dissection) in connection with 

 these sterile females, was, that I had never seen any signs 

 externally of ova. There was a very good morphological reason 

 for this, ijecause even supposing that any ova had been extruded 

 — and I have pointed out that this is impossible — they must 

 inevitably have been lost, as the hairs clothing the pleopoda, 

 though of similar structure to those of the female, are rudimen- 

 tary; so that no ova could have become attached to them. The 

 three reasons which I have already given ( 1 st, inability to extend 

 the pleon to allow of fecundation taking place; 2nd, rudimentary 

 state of the vulvie; 3rd, rudimentary state of the ovigerous hairs, 

 conclusively demonstrate that this form as it is'^' is absolutely 

 incapable of reproduction. Here, it may be stated, that up to 

 a fairly large size, viewed dorsally, it is impossible to discriminate 

 between males, females and sterile females. After this stage is 

 passed, the chelipeds of the male become comparatively much 

 larger, attaining considerable proportions. The sterile females! 

 do not become any larger, and in comparative size of chelpe and a 

 few other general characters, resemble the female, excepting that 

 the female's body may reach as great a size as that of the largest 

 male. 



Ten years ago, in the Proceedings of this Society,! Pi'of. Haswell 

 described a case of Saccidina infesting one of our semi-pelagic 

 species, S ectocarcinus integrifions. Only male specimens were 



* I emphasise "as it is" because I fully believe that this form, under 

 certain circumstances, is capable of changing into a perfect female; in 

 which case it would, of course, be capable of reproduction. 



t Though for convenience, I have adhered to the term " sterile female," 

 I would not be at all surprised if it should transpire that all the perfect 

 females pass through this stage. Should this be so (and it can only be 

 verified by examining a great many specimens of a very small size), the 

 term would need to be altered to "immature female." Notwithstanding 

 this, I consider it by no means certain that all of these forms would undergo 

 that change, as I have found some of them considerably larger than the 

 smallest ovigerous female. 



: P.L.S.N.S.W. (2), Vol. ii. 1888. 



