SCIEXCE-GOSSIP. 



SPAWNING OF COMMON SOLE. 



-lyTR. GERARD W. BUTLER, B.A., con- 

 tributes to the "Journal of the Marine 

 Biological Association of the United Kingdom," 

 issued in September last, some valuable notes upon 

 the spawning of Solea vulgaris, in the Association's 

 Aquarium at Plymouth, during April and May of 

 this year. So far as is recorded, this is the first 

 occasion on which these fish have been known to 

 spawn in captivity. Mr. Butler obtained un- 

 fertilized eggs on April 3rd and 7th, and on 

 the 1 2th fertilized eggs were found for the first 

 time. Again on April 20th and 21st, only un- 

 fertilized ova were taken. From that time forward 

 during the rest of his stay at the laboratory, fer- 

 tilized eggs appeared, sometimes on two con- 

 secutive days, at other times with intervals of from 

 one to two days, sterile eggs being the exception. 

 The time of day at which spawning occurred seemed 

 to get earlier with the increased temperature of the 

 weather. During the last week in April, the eggs 

 were in the first segmentation stage between 6 and 

 7 p.m., subsequent observations pointing to their 

 having been spawned about 4 p.m. ; later on the 

 egg-laying began about noon. Examination of the 

 ovaries of one of the females, which was sacrificed 

 for histological study, proved that the spawning 

 period extends over three months or so. In this 

 specimen the ova were of all sizes, the largest and 

 most transparent are presumably those nearly 

 ripe, being distributed singly among those less ripe, 

 and they did not seem to be confined especially to 

 one region of the ovary. 



During the act of spawning the soles lay about 

 the bottom of the tank apparently indiscriminately, 

 and there was nothing to indicate anything in the 

 nature of pairing. Each fish leisurely moved 

 from one point to another, and appeared preoccupied 

 only with its own share in the operation. In 

 spawning, the sole lay on the sand, and raising its 

 head brought it down again with force, the action 

 agitating the whole length of the fish. The eggs 

 appear to be shed one at a time, the vibrating 

 movements being apparently to waft the egg 

 clear of the fish. On three occasions when Mr. 

 Butler attempted to obtain ova from the living 

 fish failure was the result, but as these fish appear 

 to deposit only a small number of eggs each 

 day, it may have happened that he had not 

 selected the right moment for their extrusion. 



Captured eggs spawned in a tank on April 28th, 

 hatched out in numbers on the seventh day, but 

 eggs spawned a week later and thence onwards 

 hatched on the fifth day, one degree of temperature 

 higher being recorded in the water. The period of 

 development of the young animal in the ovum is 

 evidently largely controlled by temperature, being 

 hastened bv warmth. 



A PORTABLE FIELD-GLASS. 



VT7E have received from Messrs. R. and J. Beck, 

 Limited, of 68, Cornhill, London, a most 

 ingenious pair of opera-glasses, which fold up into a 

 space that will occupy no more than a lady's card 

 case. They are, in fact, called by Messrs. Beck 

 " The Card-Case Opera-Glass." 



The Glass when open for use. 



To naturalists they will be invaluable on account 

 of their portability and lightness; when folded they 

 are only three-tenths of an inch in thickness. The 

 difficulty of the ordinary- field-glass is its size and 

 weight. The glass before us, however, weighs only 



The Glass when folded. 



three and a half ounces, this being due to the 



absence of tubes in conjunction with the lenses. 

 We have tried these glasses and find they will be 

 equally useful for field work, the museum, and for 

 the theatre or picture gallery. 



