98 



Part III. — Twenty-third Annual Report 



The Effect of the Exposure of the Lobsters to Strong Light. 



A number of lobsters have been kept out of doors, in tanks which were 

 without covering. In two of the tanks the bodies of the lobsters were 

 hidden by the wooden shelf which formed the common roof to their pens ; 

 one large concrete tank afforded them no cover whatever. In the former 

 the antennae of the inmates were exposed to direct daylight, and they 

 very often had pieces of seaweed and smaller ectozoa growing on them 

 during the summer. Two females were kept in the concrete tank from 

 the autumn of 1902 till September 1903. At the latter date they were 

 completely covered and hidden by a prolific growth of seaweeds, 

 Laminaria sp., young mussels, &c, which completely occupied the 

 dorsum of each shell-fish (vide fig. 73, pi. iv.). The covering appeared 

 to be of some inconvenience to the lobster in walking. While the 

 growth of the seaweeds was, no doubt, directly due to the exposure to 

 daylight, it is probable that it was permitted by the host as a shelter in 

 the exposed tank. The shells of the pair were clean when they were 

 put into the tank. Herrick records examining a number of lobsters 

 which were adorned with more or less extensive collections of seaweeds 

 and other ectozoa. On none of the lobsters captured in the sea and sent 

 to the Laboratory was there any coat of seaweed. The ectozoa usually 

 consisted of tubes of Serpula sp., Balanus sp. One of the two cast its 

 shell on 19th October 1903, and a drawing has been made from the cast 

 shell (fig. 73, pi. iv.). It lived until May 1904. The other lobster did 

 not cast, but remained covered with seaweed during the winter ; it also 

 was found dead in May 1904. 



Body Fluid. 



The body fluid of the lobster is richly albuminous. It is colourless 

 when fresh, but soon congeals on exposure to air to a clear jelly with a 

 slightly blown tint. Alcohol (94 per cent.) causes the blood to 

 coagulate at once. 



Dissection. — Examination of the Ovary. 



Almost without exception, the ovaries of the lobsters examined, 

 measuring 9 inches and over in total length, were found to contain eggs as 

 large, or nearly as large, as ripe eggs. When the eggs are large, yolked, and 

 approaching ripeness the ovary is black in colour ; the eggs themselves 

 are black, although the yolk is really a very dark-green colour. The 

 ovary turns red in alcohol. 



The lobsters were broadly distinguished as (a) berried, (b) lobsters 

 which had lately hatched their eggs, (c) soft. 



(a) Berried Hens. 



(1) December 21, 1904. — A lobster (from Dunbar) measured 

 1 1 j inches in length. The shell was clean. The external eggs were black, 

 showing no pink-coloured part, simply a light-green formative part. The 

 eggs were evidently early. The ovary was white, but contained green 

 eggs measuring *4 and "5 mm. The smaller green eggs contained simply a 

 core of green yolk, surrounded by a periphery of white yolk (by trans- 

 mitted light). The oviducts were filled with a greenish fluid. 



(2) February 19, 1905. — In a lobster (from Dunbar) the external eggs 

 were well advanced ; the pink area was about one-fifth of the whole egg. 

 The ovary was large and black in colour. 



