324 MESSRS. C. SHP:ARER, W. DE MORGAN, AND H. M. FUCHS 



roughly with the temperatures of the water of the open sea, the Sound water 

 invariably showing a much greater range of variation than that of the Channel. 

 They will for this reason hardly apply to E. esculentus and E. acutus, but vrill apply 

 directly to E. miliaris, in which species we consider that the germ cells (at least 

 those of the female) had been affected. 



As we have mentioned, the mass of our E. miliaris material was obtained from 

 Cawsand Bay, one of the smaller divisions of Plymouth Sound. The temperature 

 variations at Cawsand are about the same as those shown in our curves, with the 

 possible difference that extremes will be more marked. In Cawsand Bay, E. miliaris 

 is found in shallow water close to the shore, and will be readily affected by any 

 variations of the land temperature. It is well known that Cawsand is much the 

 coldest part of Plymouth Sound. We may assume, therefore, that temperatures 

 obtained from the end of the Pier will certainly not show a greater amount of 

 variation than at Cawsand.* 



In text-fig. 17 are shown together the temperature curves of the four seasons. 

 They start from the first week in September, and are continued to the first week 

 in June. 



With regard to E. miliaris, which breeds so much later than E. esculentus, it is 

 probable that little variation of the sea temperature would affect the germ cells 

 before the middle of January. The period of the growth of the germ cells in this 

 form is from the middle of January to April 1, so that any temperature changes 

 before or after this can be neglected. 



It will be seen from an inspection of text-fig. 17 that the curves 1 and 2, repre- 

 senting the seasons of 1908-9 and 1909-10, are very similar in all respects. No. 2 

 represents a somewhat colder year than No. 1. Their resemblance is very close, 

 especially for the important period from the middle of Januaiy onwards. With 

 No. 3 the two preceding curves show much less resemblance. No. 3 is exceptionally 

 low throughout the latter part of its course. 



No. 4, representing the season of 1911-12, is the most remarkable of the four, 

 going directly downwards from the highest to the lowest record, on January 1. In 

 the important portion of the latter part of its course it is very much higher than 

 the others. The two extremes of temperature are thus shown in Nos. 3 and 4. But 

 it was in these years we found the change in inheritance ; it is possible that this 

 difference In the extremes of temperature may have some connection with this 

 change. It will be seen that from March 1 to June 1 there was almost a difterence 

 of 4° F. between the water temperature in these two successive seasons. Whether 

 this variation of temperature had a direct influence on the inheritance in our 



* In 1911 and 1912 a considerable amount of our £. miUaris material was obtained from Wemburj' Bay. 

 The temperature conditions in Cawsand and Wembury Bay are much the same, so that what applies to one 

 will applj' also to the other. Minor variations of temperature would be possibly less marked in Wembury 

 than in the more land-locked region of Cawsand Bay. 



