of the Fishery Board for Scotland. 



101 



Ehrenbaum, but extends it to the middle of October. Meek found newly- 

 spawned lobsters in July and August. The lobster which spawned during 

 Cunningham's experiments in Cornwall did so in October, and Scott's 

 specimen extruded its eggs during the same month at Piel Laboratory. 



There is thus indicated an extended spawning season, including the 

 months of July, August, September, and October. It may be that there 

 are here two distinct groups of spawners — summer and autumn spawners — 

 the first including lobsters that were not berried during the winter 

 immediately preceding, while the autumn spawners are those which were 

 berried during the winter, hatched their eggs in the summer, and extruded 

 another batch of eggs in the autumn. 



The question whether or not the European lobster may carry external 

 eggs two years in succession does not arise, Cunningham's observation, 

 confirmed later by Scott's description of the process, having demonstrated 

 that possibility. As for the American lobster, Herrick maintains, in a 

 later work, the position taken by him on this question in 1895. He 

 founds his contention that the American lobster does not carry eggs 

 externally two years in succession on the condition of the ovary in various 

 lobsters which had lately hatched the eggs. He maintains that the ovary 

 requires two years to develop to ripeness. 



The factors which determine the spawning of the lobster are obscure. 

 It is remarkable that only one lobster spawned in the Laboratory, 

 although in several cases the ovaries of specimens which were dissected 

 were apparently ripe. The rate of development of the ovary is dependent 

 on some factor that is not apparent. The ovaries referred to would 

 probably have been completely ripe in a short time. The complete 

 ripening seemed to be inhibited by some influence, which might have 

 been the absence or insufficiency of male lobsters. Even where a male 

 lobster was present with the female spawning did not take place, and 

 when the one lobster spawned no male was present. Otherwise the 

 lobsters, it may be inferred, were under comparatively suitable conditions, 

 for there was an uniformity shown in their history while in confinement. 

 Moulting was common. What is the reason for the abstention from 

 spawning? The artificially-supplied food may have induced growth 

 rather than reproduction. 



The lobster may spawn the same year in which it has cast its shell. 

 Trybom's experiments* in labelling lobsters in order to determine their 

 migrations indicated two females, measuring 8| inches long, liberated in 

 June, had in November cast their shells and spawned ; they then measured 

 a little over 9 inches in length. 



The actual modus of spawning has been described by Coste, Scott, and 

 others. 



Ehrenbaum describes a condition of the lobster which follows when a 

 ripe lobster has been prevented from spawning. The eggs are absorbed 

 and the blood becomes dark green or black in colour. The dark blood 

 shows through at certain parts of the body and the lobster is known as a 

 black lobster. Lobsters in this condition are found among those con- 

 fined in floating boxes. The ovaries are much reduced in size, and the 

 majority of the eggs have lost the green yolk, and have become of a 

 yellowish colour. 



The Ripe Egg and the Formation of the Perivitelline Space. 



The ripe egg, newly spawned, was measured by Scott and found to be 

 l-8mm. in diameter. 



*Fish Trades Gazette, July 30, 1904. 



