200 PRELIMINARY INQUIRIES AT PLYMOUTH INTO 



west by south of the Eddystone. There were not many in 

 the trawl, and although I got a few ripe ova, I could not 

 press any milt from any of the fish. Accordingly, when I 

 got ashore again I found the ova were unfertilized. Nearly 

 all the trawlers after this time went to fish off the Wolf 

 Rock, about thirty to forty miles west of the Lizard, remain- 

 ing at sea a week on each trip. In oi^der to pursue the 

 study of soles' ova, I went several times with one of them 

 in March, April, and May to this fishing ground, where soles 

 are very much more abundant than off Plymouth. But 

 although I frequently obtained ripe ova in considerable 

 numbers, I could never press out ripe milt from a male. I 

 therefore cut out the testes and cut them in pieces and 

 placed them in the water with the ova, hoping that fertili- 

 zation could be effected by this method. The expedient suc- 

 ceeded, but only to a slight degree, as only about a dozen 

 ova were fertilized on each occasion out of several hundreds. 

 These few were sufficient to show the normal character of 

 the fertilized ova. The ovum of the sole was thus found to 

 have several marked peculiarities, which enable it to be 

 recognised with certainty when taken in the tow-net. It 

 is of considerable size, and spherical in shape ; instead of 

 having a single oil globule it has a large number of very 

 minute size, which are irregularly distributed in groups of 

 different sizes over the surface of the ovum. The vitellus is 

 homogeneous in the centre, but when the embryo is formed 

 has a superficial layer of separate vitelline masses. 



The ova of the merry-sole, Plenronectes microcephalus, 

 were obtained with great ease in large numbers and ferti- 

 lized without difficulty. Numbers of these were hatched, 

 although they were kept in small bottles, in which the water 

 was changed only once a day. If it were worth while to 

 propagate so abundant and cheap a form, it would be a 

 simple matter to hatch millions of young merry-soles from 

 the eggs of the parent fish caught for the market. 



The eggs of two species of gurnard, Trigla gurnardus and 

 Trigla cuculus were also fertilized, and the young fish hatched; 

 but these were not so hardy as those of the merry-sole. 



The ova of the mackerel are at present under observation. 



