192 



The egg <^ Plate I, fig. 16 j has fairly well developed 

 characteristics, being large, destitute of an oil globule, and with 

 a series of striations and spots on its surface. It is also 

 characterized by a cluster of clear thread-like markings as if 

 hanging in a loose network from the under-side of the germinal 

 disc down nearly half way into the yolk. 



The mature females were found to vary considerably in size, 

 and a good opportunity was afforded of ascertaining the 

 relation, if any, between the size of the egg and the size of the 

 female. Thus in one haul three perfectly ripe females were 

 procured measuring 146, 117, and 96 millimetres respectively. 

 The diameters of 25 eggs from each were determined with the 

 following results. — 



Length of female ... ... 146 mm. 117 mm. 96 mm. 



Average diameter of 25 ova. 97 ,, 



Maximvmi ,, ,, ,, ... "98 ,. 



Minimum ,, ,, ,, ... '94 ,, 



With the exception of the maximum and minimum of the 

 eggs of the smallest specimen this table shows a distinct pro- 

 portion between the size of the egg and that of the parent. 

 The maximum in this particular case is greater than the 

 maximum of the largest specimen, and the minimum 

 equals that of the 2nd largest. An examination of the 

 actual measurements, however, in a manner explains this. 

 The measurements wert taken of the first 25 without selection, 

 and as only one single egg was found of this very large size 

 (1-02 mm.), it may perhaps be regarded as abnormal. The next 

 largest egg was -95 mm., which would be the usual proportion, 

 and in glancing through about 100 this large egg was very 

 distinctly of an exceptional size. As, however, it appeared of 

 perfectly normal structure and in perfectly normal con- 

 dition it was not rejected. The minimum ('91) of the 

 smallest specimen also does not represent the actual 

 proportions, as in the 2nd largest specimen, which has 

 the same minimum, there was only one (^f this size, while in 

 the smallest specimen there were four. There is certainlv 

 evidence from these measurements indicating a general relation 

 between the size of ova and parent. 



An opportunity was afforded on another occasion of 

 measuring 100 eggs of another specimen of Achirus ^i a 

 normal size, about that of the largest specimen mentioned 

 above. The average size was -97 mm. and they ranged from 

 •99 to '94. Fertilization was attempted at 12.10 p.m. by 

 shaking up teased testes among the ripe eggs, but by 6 p.m. 

 they showed distinct signs of disintegration, and most had left 

 the surface and lay on the bottom of the jar. 



