OBSERVED AT PLYMOUTH IN THE SPRING OF 1902. 605 



On March 19th I agam obtained a single egg with copper-coloured 

 globule, but it also failed to hatch. 



Holt obtained eggs with colourless, " and some few with distinctly 

 cupreous globules," from one specimen of M. mustela, so that the 

 colour, not being present in all the eggs, is evidently not character- 

 istic ; and from the fact that out of perhaps twenty-five eggs with this 

 distinction I could not get one to hatch it occurred to me that the 

 colour might be indicative of some pathogenic condition. Un- 

 fortunately material did not suffice to make further investigations 

 on this point. 



The eggs with the green oil globule always developed normally, pro- 

 ducing a larva with the same character but otherwise quite similar to 

 larvpe hatched from eggs with the colourless globule. This was as Holt 

 found. 



On several occasions I have come across eggs with a large number 

 of colourless oil globules of various sizes, the eggs having a perivitelline 

 space, but never showing any signs of development. The globules in 

 many cases ran together in the course of a few days, but the eggs were 

 infertile. Holt also found these eggs and obtained them directly from 

 a female Motella mustela. 



On April 9th a ripe female Motella 19 cms. long was brought to 

 me, which proved to be a specimen of M. fusca (Moreau), a description 

 of which will be found on another page. Large numbers of eggs had 

 been extruded in the handkerchief in which the fish was carried, and 

 many more were obtained from the fish by slight pressure. These eggs 

 exactly agreed with the infertile eggs above referred to. The size 

 varied between '69 and '82 mm. diameter, the majority of those 

 measured, however, being about 72 to -74 mm. ; and the oil 

 globules, in a few in which only one was present, measured 13 

 to '14 mm. 



Brook gives the size of fertilised eggs of M. mustela as "65 to 'lo 

 longer axis, and '64 to "716 shorter axis with an oil globule of 

 about "11. The eggs of M. fusca, therefore, appear to be slightly 

 larger, with a larger oil globule than those of the former species, but 

 there is probably not sufficient difference to distinguish between 

 tow-net eggs. 



Holt found the size of the eggs with a greenish globule, which lie 

 mentions in his Irish papers {Trans. Boy. Buhl. Soc, ii. (1891), p. 464, 

 and V. (1893), p. 95) as -66, with o.g. 14, and 72, o.g. 17, and I find 

 that those I have obtained this year here vary between '69 and "82, 

 o.g.'s 14 and •20. The eggs with the colourless globule vary from 

 70 to -87, o.g. 12 to 19. 



Unless, therefore, the green oil globule can be taken as a specific 



