34 



the female crabs which had not migrated the ova were small in 

 size, whereas in the females which had migrated the ova were 

 approaching the size of maturity. This tended to prove (1) that 

 the migration was due to the development of the ova, and (2) 

 that the condition cf the ova in the non-migratory females pointed 

 to a postponement of the spawning season. Besides in our experi- 

 ence no matter how large the crab hatching almost invariably is 

 succeeded by an ecdysis. 



If this latter aspect of the condition in question be found to 

 be the general one it is evident that the ripening of the gonads does 

 not take place in such cases until the approach of the spawning 

 season., that is to say, according to the conditions given in the chart 

 until in the one when nearly nine and in the other approaching 

 thirteen years. Furthermore it is clear that not merely the rate 

 of growth is slowing down but in association therewith the ripening 

 of the ova takes place at a longer interval of time. It is admitted 

 that in some cases reproduction may take place as has been stated 

 twice during the instar when the instar is a long enough one to 

 permit it, but it is manifest that the periodicity of the ripening 

 is controlled by somatic growth, or rather that ripening is slowing 

 down in association with the decline in growth. It may yet be 

 shoAvn that subsequent to the age considered four years may elapse 

 before spawnmg takes place. Even if it be said that two spaw^iings 

 may occur in the instar, it is evident that the sperms have a much 

 longer period of life in the spermatheca than has been in this and 

 similar cases considered. 



We have thus an interesting correlation between growth, 

 ecdysis, reproduction and migration. With reference to the last 

 it is not necessary to state after the work which has been reported 

 upon before, that it only affects the females. 



There is one further point relating to the migrations which 

 may be touched upon here although it is not the intention to 

 dwell on this aspect of the subject. The question has been asked, 

 is there a return migration of the females ( It is not at all likely 

 to be general if it occur at all, for if the above considerations be 

 accepted, it is apparent that after migrating contranatantly and 

 spawning and hatching, the female \dll cast in the new situation. 

 The evidence goes to show that until she gets the impulse to move 

 on again she remains where the ecdysis took place, and further 

 when she migrates again it is still further in the same direction. 



