IN THE SOUTH-WESTERN DISTKICr. 129 



a little later than the others. So far as the few recorded observations 

 go, there seems to be no possibility of distinguishing their eggs by 

 dimensions alone. Thus, from a single example of each species, the 

 various authors who have dealt with them give the followinfj sizes : — 



Bh. pundatas, unfertilised . . d. 1-05 ca. e.g. 0*20 mm. ca. 



Rh. norvegicus, „ . . „ '90 „ 'lo „ 



P. unimaculatus, „ . . •92-93 ,, (•1G-"18) mm. 



Fertilised ova from the last specimen measured from "90 to "99 mm. 

 in diameter, the oil-globule from '16 to "18 mm. 



If the fertilised eggs of a single parent show a variation inter se of 

 "09 mm., it is more than probable that the variation of the eggs of the 

 species as a whole is really much greater. For F. unimaculatus, Brooks' 

 measurement of the ripe ovarian egg, after preservation, is '96 mm. 

 Without further words, I think it will be plain that the eggs of the 

 three species overlap each other in so far as dimensions are concerned, 

 although in all probability the egg of Rh. inmctatus is on an average the 

 largest, that of Rh. norvcgicus the smallest of the three. Such compara- 

 tive sizes of the eggs conform to those of the parent species, so far as 

 they are known to me. 



The eggs taken in our tow-nets may be recapitulated as follows, the 

 dimensions of each individual egg being given : — 



The egg of June 4th, only observed in its early condition, belongs 

 perhaps more probably to Capros aper than to a Topknot. 



With regard to the rest it appears at first sight possible to select two, 

 measuring ^90 and ^91 mm. in diameter, as dillering markedly from the 

 rest; but it is necessary to remember that the dillereuce of •IS mm. 

 which separates the smallest of these two from the largest of the whole 

 series is no more than is met with in a single species having ova of 



