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1300 — 1500 eggs within the space of 15 minutes. However this claim 

 is somewhat in doubt since Lovén^ the following year maintained that 

 this same species deposits its eggs in groups of 7 — 16 on stones. Many 

 years later Metcalf (1892)3 made observations on Chiton sqa?nosus and 

 Ch. marmoratus which were confined in an aijuarium where first the 

 males, like Mopalia lignosa (cf. Heath* 1899. p. 572), shed the sperm 

 after which the eggs are laid. In the case of the last named species the 

 females shed the sex products only after the sperms had diffused to them, 

 at times over a distance of ten or even twenty feet, and the fact that 

 Ch. squamosus and Ch. marmoratus deposited their eggs from 1 — 1 V2 

 minutes after the spermatozoa were liberated leads to the conclusion that 

 here likewise the sex products or some additional substance are essential 

 to produce the necessary stimulus. By way of experiment I have kept 

 solitary individuals of Mopalia lignosa and Ischnochiton magdalenensis 

 in small elevated tide pools, which during the summer are usually aerated 

 by algae and not by the dash of the surf as in the winter months, and 

 of the twenty-three individuals the males invariably shed their products 

 while the females, with one exception, retained theirs beyond their usual 

 breeding time for six or eight weeks when the experiments were terminated. 

 In control experiments where males and females were associated the sex 

 products were liberated in the usual way. 



During the past few years I have seen the egg laying process of 

 Ischnochiton mertensii^ Isch. cooperi^ Mopalia muscosa and Katharina 

 tunicata which were inhabiting some of the larger pools isolated during 

 low tide from the open ocean in the vicinity of Montery Bay, California. 

 During this period of tranquility the males, always perfectly quiet, 

 liberate spermatozoa steadily or with short intervals until disturbed by 

 the dash of the returning surf. In some cases the process may comsume 

 two hours but usually not over half of this time. Almost immediately after 

 the spermatozoa have diffused into the vicinity of the females, and in one 

 case [M. muscosa) before the eye was able to detect its presence in the 

 immediate neighborhood of the female, the eggs commenced to escape 

 freely from the oviducts. In the case of Katharina a mucous secretion 

 unites the eggs slightly but the development of albumen glands is far 

 inferior to that of Ischnochiton magdalenensis and within a short time the 

 ova are widely scattered in tidal currents. 



On some of the rocky headlands and in the previously mentioned 

 tide pools Trachydermon raymondi and Nuttallina thomasi are compa- 

 ratively abundant and as in the case of Chiton polii according to Kowa- 



2 Lovén. S., Über die Entwicklung von Chiton. Arch. Naturgesch. Bd. 1. 1856. 

 ■^ M et calf, M. M., Preliminary notes on the development of the Chitons, 

 Johns Hopkins Univ. Circ. XI. 1892. 



4 Heath, H., The development oî Ischnochiton. Zool. Jahrb. Bd. XII. 1899. 



