THE AMERICAN LOBSTER. 91 



formation of the stones is arrested, as Chantraii had often observed in October and 

 November, the crayfish was unable to molt, and died. 



Chautran (42) presented to the Academy of Sciences of Paris a paper, giving an 

 account of the natural concretions, called " crayfishes' eyes, 1 ' produced from the time 

 of birth in this crustacean up to the age of six years — that is, during 22 successive 

 molts. It was found that the stones are not absorbed at the moment they become free 

 in the stomach, but that they are gradually worn down by reciprocal rubbing and 

 contractions of the stomach. The plane faces of the stones are thus rubbed together 

 until they are gradually woru down, and at the tenth hour after ecdysis they are 

 reduced to pellicles of 1 to 2 mm. in diameter. The destruction of the concretions 

 may be complete at this time, or they may persist up to the eightieth hour. 



According to Chantran (41, 42), the number and succession of molts in the Euro- 

 pean crayfish are as follows: First year, 8; second year, 5 or 6 ; third year, 3. After the 

 third year the males molt twice and the females once annually. He further believed 

 that every molt involved the formation of calcareous masses in the stomach, and that 

 these numbers consequently show how often the gastroliths have been formed and 

 used up. The time occupied in their formation increases with age, being 10 days the 

 first year, 15 days the second, 25 days the third, and 40 days in subsequent years. 

 The time which elapses after the molt before the stones are reabsorbed also varies 

 with the age of the individual, from 24 to 30 hours in the young, which have not 

 molted more than twice, to from 70 to 80 hours in adults. 



HISTORY OF THE GASTROLITHS — THEIR PROBABLE FUNCTION. 



The gastroliths were the subject of much curious speculation among the older 

 naturalists — Gesner, Bellonius, and Agricola — who, according to Herbst, assigned 

 to them a position in the brain. Van Helmont, who first described their true position, 

 was not far from right in thinking that they were formed by a milky secretion which 

 was poured out between the old aud new linings of the stomach. Geoffroy's observa- 

 tions (74), published in 1709, were the best made up to his time. 



I have opened [Geoffroy says] vigorous crayfishes which had entered upon the process of molting 

 and have found in the place of each stone ascale or white plate, which swims in the middle of a mucus, 

 and which was apparently the undeveloped condition of the stone. This stone and the glairy liquor 

 were enveloped in a small, membranous, aud very delicate sac. 



In crayfishes which have recently molted the stones are not in their usual places, 

 but lie in the stomach, joined together by their concave parts. No vestige of a stone 

 was found in the stomachs of crayfish in which the shell had hardened after molting. 

 He concludes however that the stones play no part in the formation of the new shell, 

 although they appeared to serve as food after the molt. 



Keaumur (162), besides repeating Geoffroy's observations, added much that was new 

 to the subject, and placed the general facts of the molting of Crustacea beyond the 

 doubts which had existed up to his time. By dissecting crayfishes which had molted 

 he found that the stones gradually dwindled and disappeared. He says: 



Is it not natural to suppose that these stoues are dissolved, and that their substance is then 

 carried anil laid down in the interstices of the fibers of which the skin is composed ? 



Boesel (168), in his beautiful Insecten Belustigung, published in 1755, discusses at 

 some length the function of the gastroliths, coming to the conclusion that they are 

 useless material which is formed during the molt, to be afterwards expelled from the 



