150 



with the drawing of Raffaele (± 1 mM.). They hatched in 

 9 — 10 days. 



As to the eggs of the greater weever, Trachinus draco, we have 

 only the statement by Raffaele that the ripe ovarian egg has only 

 one single oil-globule and is perfectly transparent. Of the develop- 

 ment of these eggs nothing is known. It is certainly curious that 

 our knowledge of the eggs of a fish by no means rare and 

 spawning near the shore is so scarce, and the more so while 

 artificial fertilization is, as will be shown further on, quite easily 

 to be performed and the eggs develop quite normally in a glass 

 vessel containing fresh seawater. And yet, as far as I could gather, 

 the note by Prof. Raffaele is all we know about the eggs. 



As I mentioned before, both species are found on the Dutch 

 coast. When fishing in the different parts of the North Sea with 

 the Dutch investigationsteamer »Wodan", we caught with the 

 ottertrawl Trachinus draco along the whole Dutch coast, sometimes 

 in enormous numbers. Few Trachinus vipera were caught with the 

 ottertrawl but more with a naturalist-dredge with small meshes. 

 Several times I had the opportunity of collecting the ripe eggs 

 of both species and sometimes of fertilizing them artificially. In 

 the Marsdiep outside the harbour of Helder the greater weever is 

 in times very abundant and is captured by means of a baited 

 hook attached to a line ; the lesser weever too is frequently caught. 

 Both the eggs of the former and of the latter could be procured 

 not unfrequently in June and July with the surface-townet. 



The eggs of Trachinus vipera are always very easily to be 

 distinguished from the other pelagic eggs caught at the same 

 time, by the large amount of yellow and black pigment on the 

 embryo and the yolk-sac and by the large number of oil-drops 

 of a yellow or greenish-yellow hue, scattered all over the surface 

 of the yolk (Plate Vil, fig. 1). Observed against a dark background 

 they offer, at least during the earlier stages of development, a 

 yellowish aspect that makes them recognisable even with the naked 

 eye. In later stages the intense black pigment is a good diagnostic. 



