EGGS AND LARV^ OF TELEOSTEANS. 101 



The figures given of the first processes of fertilisation and development will 

 be considered in a subsequent section. 



On Dec. 5, 1885, 1 trawled with a fine meshed shrimp trawl across the Drum 

 Sands, which are situated between Queensferry Point and Cramond Island, 

 and obtained a considerable number of young Pleuronectes limanda. These 

 were about 2 inches long, and could be identified from the semicircular curve 

 in the lateral line above the pectoral fin. Larger, nearly full-grown, specimens 

 were also taken, and kept for some time in the aquarium, where they lived 

 healthily. 



In June of the current year, Mr Ramage, who is at present studying at the 

 station, pointed out to me that the sands to the west of the laboratory were 

 swarming with young flounders. These were about £ inch long, and had 

 already reached the condition of the adult ; they showed no trace of larval 

 structures. But I was unable to identify these young fish, as the lateral line 

 could not be clearly distinguished. It is of course probable that the young of 

 many different species are present in such situations in the summer months. 

 It is pretty certain that nearly all our valuable flat-fishes pass the early post- 

 larval stages of their existence on littoral sand-flats. Mr Geokge Brook 

 informs me that large numbers of young flat-fish are destroyed by shrimpers 

 in such situations. With regard to this particular locality, I have never seen 

 any shrimping carried on in the neighbourhood. 



6. Pleuronectes cynoglossus, Linn. (Witch) (PI. III. figs. 7-9 ; PI. IV., PI. V.). 



Of the developing eggs of this species I made a particularly careful study, 

 with. the intention of obtaining, if possible, greater certainty on the various 

 points in dispute concerning the earliest changes that the mature ovum under- 

 goes after being shed. A number of living specimens of the fish were trawled 

 by the " Medusa," on 23rd and 24th June of the current year, at a place called 

 Fairlie Patch, opposite the town of Fairlie, in the channel between the island 

 of Cumbrae and the mainland. The fish were taken alive to the little labora- 

 tory known as the " Ark," which was originally a floating structure, but is now 

 firmly established on the beach at the east side of Millport Bay. I have given 

 a large number of figures, illustrating the successive stages in the development 

 of this species. After the formation of the perivitelline space they are 1*155 

 mm. in diameter. The yolk is perfectly transparent, but the zona radiata is 

 thicker than in most of the other species of the genus. The perivitelline space 

 is very small. During the time the eggs were under observation the weather 

 was very fine, and the laboratory being fully exposed to the sunshine, became 

 in the middle of the day very hot. I had no means of regulating the tempera- 

 ture of the water containing the eggs, and on two occasions it rose to 20° "5 C. 



