OCCQREING IN THE NEIGHBOURflOOD OF PLYMOUTH. 25 



of Solea vulgaris. In one point the descriptions and figures of 

 Arnoglossus laterna given by Day in his British Fishes, and by 

 Giinther in his Catalogue of the British Museum Collection are a 

 little too vague. The latter author does not of course give a figure 

 for each species, and he speaks of the anterior curve of the lateral 

 line in this species is subsemicircular. The former describes it as 

 almost semicircular, and figures it as a rounded curve much like that 

 of Zeugopterus. The anterior part of the lateral line in reality forms 

 almost three sides of a square, and has another smaller curve still 

 farther forwards, as shown in outline in fig. 39. 



Eaffaele states that the mature ova of Arnoglossus are •.60 to "70 

 mm. in diameter, with a homogeneous yolk and a single oil-globule, 

 and cannot be distinguished from those of Rhomboidichthys and 

 Citharus, genera of Pleuronectids occurring in the Mediterranean, 

 but not in Britain. It would seem therefore that the ova of Arno- 

 glossus only differ from those of Rhombus in size. 



Two species of Zeugopterus occur at Plymouth. I have met with 

 a specimen of Z. punctatns taken in a lobster pot. They have no 

 value in the market and their ova are not known. 



Scomber (the Mackerel). 



My first examination of living mackerel was made on board a boat 

 called the " Prima Donna,^' on May 24th, 1888. On this occasion the 

 nets were shot on the east side of the Eddystone, about fourteen 

 miles from Plymouth Sound ; and when they were hauled at day- 

 break in their whole length of nearly two and a half miles only 

 about fifty mackerel were taken. Several of these were males in a 

 perfectly ripe condition, but only one ripe female was found, from 

 which a number of ova were taken and fertilized. The skipper and 

 the men having seen performed the simple operations necessary to 

 obtain and fertilize the eggs, I left a basket of collecting bottles on 

 board, and they supplied me with fertilized ova almost every time 

 they went to sea. In fact, by this skipper and another, who was also 

 taught how to collect them, more ova were sent to me than I could 

 deal with, and I had to tell them not to send any until I gave them 

 notice. The spawning continued from the end of May till the middle 

 of July, and throughout this time I was studying and making experi- 

 ments with mackerel ova. I received the last of the season on July 

 17th. It follows from this that mackerel in the neighbourhood of 

 Plymouth spawn principally in June and the first half of July, that 

 the ovaries and testes of all the adult' fish become ripe within this 

 period, and that all the reproductive products in a given fish are 

 matured and shed within a short space of time. The process of spawn- 



