572 HAROLD HEATH, 



specimens that continued laying in the laboratory showed the rate to 

 be 7 inches per hour, occupying, if this rate be normal and uniform, 

 nearly five hours in laying egg strings 31 inches long. 



In many cases the strings are found in the greatest profusion 

 attached to the seaweeds (fucus, corallines etc.) that cover the rocks 

 in this region. It may be that they were placed there directly, or 

 were washed into this position; I cannot say which method obtains, 

 but I am inclined to the latter, since the Chiton when laying in the 

 aquarium are perfectly quiet. The egg strings are not fastened, 

 simply caught on the leaves and stems, and the heavy waves wash 

 them away and break them into fragments so that it is scarcely 

 possible on the next day to find pieces longer than one or two inches, 

 and after a week has elapsed almost all traces have disappeared. 



The Chitons along a considerable extent of coast, lay on the 

 same day. For example, on the morning of June 9th eggs were found 

 along a quarter of a mile of coast; on June 13th over a somewhat 

 larger area; and on the 23rd for more than a mile. In each case a 

 large number of specimens were examined and all were found to have 

 shed their genital products. In tide pools, as I once observed, females 

 of Mopalia lignosa, though distant several feet from the males, will 

 lay almost as soon as the sperm difiuses to them: the same is true 

 of a species of Polychaete (probably Cirratulus) of the west coast. 

 It may be that in the case of Ischnochiton one of the reasons the 

 eggs are laid at the same time in such definite localities is owing to 

 the diffusion of sperm by the tidal currents, though the fact that all 

 are subjected to similar conditions, e. g. quietness of water, time of 

 month or year, temperature, must be of high importance. 



By compressing portions of the egg string one half inch in length 

 under a ruled cover glass , and counting the eggs , a very close 

 estimate of the total number laid by each individual may be made. 

 This was done in several cases, and gave 821, 935, and 1561 as the 

 lowest, average and highest number. Considering that every Chiton 

 lays two strings each with an average length of 31 inches, the total 

 number of eggs laid in the above examples is 101 8U4, 115 940 and 

 193564. 



Despite the fact that such a vast number of eggs are laid, only 

 a very few develop into adult Chiton. A careful search six months 

 after the egg laying season will reveal but a relatively small number 

 of the young, which by this time have reached a total length of about 

 8 mm. What has been said for Ischnochiton in this connection, bears 



