of the Fishery Board for Scotland. 



8*7 



of a female whose brood had just been hatched did not appear to me in 

 itself to offer evidence for or against the view that eggs would not be 

 laid during the summer. ... If no further evidence of a different 

 kind wore forthcoming one would, I think, have been inclined to expect 

 that the eggs would have been laid during the same summer." Prince* 

 combated the theory of biennial spawning on histological and other 

 grounds. In a footnote (p. 72) Herrick adds — "The best w T ay to test 

 the question by experiment would be to take a female which had recently 

 hatched a brood, and keep her alive until the foJ lowing summer, when the 

 next batch of eggs would be due, in case the spawning period is a biennial 

 one." This has been done by Cunningham,t and the result of the 

 experiment has been to disprove the contention of Ehrenbaum, Herrick, 

 and Fullarton. Of five lobsters which had hatched their eggs, and which 

 were put into a floating box in September, one was berried on October 

 1 4th ; another examined on February 9th evidently had a ripe ovary, 

 but having apparently failed to extrude the eggs, the latter were being- 

 absorbed. Two of the remaining lobsters cast their shells ; the fifth 

 escaped from the box. These facts, then, point to the conclusion that, 

 as in the case of the crab, the lobster may carry eggs two years in suc- 

 cession. The lobsters which Herrick dissected were probably about to 

 cast, and when growth is taking place the ovaries would appear to be 

 quiescent. The crab will not, I believe, prepare for casting so long as a 

 supply of sperms remains in the spermatheca ; in other words, it will 

 keep on having successive batches of eggs until the supply of sperms 

 is exhausted. J A crab on casting throws off the inner lining of the 

 spermatheca and vagina in addition to its exoskeleton, and therefore 

 the contents of the spermatheca are also discarded at that time. The 

 presence or absence of sperms is what decides the direction in the 

 former case of the nourishment to the ovary; in the latter to the general 

 tissue, and especially the subdermal areolar tissue. This is, no doubt, 

 what takes place generally ; but the absence of sperms from the sperma- 

 theca does not in all cases prevent the development of the ovary. Thus, 

 two crabs with empty egg-capsules, one 4J inches, got in October, and 

 another 6^ inches in December, had red ovaries which were practically 

 ripe, although the spermatheca showed no sperms. Another 5 T 5 ^ inches 

 (October) had an orange-coloured ovary with eggs "2mm. There was in 

 respect to certain characters some evidence that these crabs were 

 preparing to cast. Again, in one crab which was soft, mentioned above, 

 an orange-coloured ovary, with small eggs however (-15mm.), was 

 observed. Herrick mentions two cases of the lobster extruding its eggs 

 shortly after casting. In such circumstances the ovaries must have been 

 ripe before the casting. It is very probable the ripening of the ovary 

 while the crab is preparing to cast may be due to the fact that the crab 

 had had the advantage of a large food supply, and therefore had an 

 excess of nutritive material, which was laid up in the ovary. In most 

 cases it is, however, the case that the ovary at casting is little developed. 

 The stage of development of the ovary at the time the crab casts will, 

 no doubt, have the effect of shortening or lengthening the period 

 between casting and spawning. Thus, if a crab has a ripe ovary when 

 it casts, in summer, say, it would in all probability extrude its eggs 

 within the next four or five months ; whereas, if the ovary is at that time 

 very immature, spawning will not be likely to take place until after an 

 interval of about 14 months. 



* Report of the Canadian Lobster Commission, 1898 (No. 11 C), Ottawa, 1899. 

 f Op. cit. pp., 40-41. 



% Coste found that Maia sqidnado spawned twice after a single impregnation (Comptes 

 Rendus, XLVTL, p. 49, 1858). According to the observations of Mitchell recorded by 

 Miss Rathbun {Proc. U.S. Nat. Mus., XVIII., p. 369, 1895), the females of Callinectes 

 sapidus are impregnated in their third summer, after which they cease to moult, and the 

 single impregnation suffices for all subsequent spawnings. The first spawning takes 

 place in the fourth summer — a year after impregnation. 



