266 



SCIENCE. 



[N. S. Vol. I. No. 10. 



consisting of liiindreds of small spicules 

 makes the solution of them possible in a 

 very short time. 



The gastroliths have been supposed to 

 possess great medical properties and to 

 perform a variety of functions, the most 

 common and accepted belief being that they 

 play an important part in the provision of 

 lime for the hardening of the new shell. 

 The small quantity of lime which they con- 

 tain, however, not more than one one hund- 

 red and twenty-sixth of that of the entire 

 shell, according to an analysis recently 

 m.ade by Dr. Eobt. Irvine, shows that 

 this is relatively unimportant. Fragments 

 of lime furthermore are always at hand, and 

 are frequently eaten by the soft lobster, 

 shortly after ecdysis, in the adolescent 

 stages at least. It is more likely that the 

 gastroliths are the result of excretion of lime 

 which is absorbed from parts of the shell to 

 render molting possible, and that their sub- 

 sequent absorption in the stomach is a mat- 

 ter of minor importance. 



Bate of Growth. — Larvse increase in length 

 at each molt (stages 2 to 10) from 11 to 

 15.84%, or on the average about 13.5% 

 (measurements from 66 individuals). The 

 increase in the young at each molt agrees 

 quite closely with that seen in the adult, 

 where the increase per cent, in ten cases 

 was 15.3%. Allowing an increase per 

 cent, at each molt of 15.3 — probably not ex- 

 cessive for young reared in the ocean — and 

 assuming the length of the first larv£e to be 

 7.84 mm. we can compute approximately 

 the length of the individual at each molt. 



Length at 10th molt 28.23 mm. 

 " " 15th " 57.53 " 

 " " 20th " 117.24 " 

 " "25th " 258.90 " (9.5 inches. ) 

 " "30th " 486.81 " (19.1 inches.) 



According to this estimate a lobster two 

 inches long has molted 14 times ; a lobster 

 5 inches in length, from 20 to 21 times ; an 

 adult from 10 to 11 inches long, 25 to 26 



times; and a 19-inch lobster, 30 times. These 

 estimates do not, I believe, go very far 

 astray. We see them practically verified 

 xip to the tenth molt. 



The time interval between successive 

 molts is the next point to consider. Here 

 the data are very imperfect. How long is 

 the three-inch lobster in growing to be six 

 inches long ? Probably not more than t^vo 

 years and possibly less. This is supported 

 by the observations of G. Brook. We there- 

 fore conclude that a ten-inch lobster is be- 

 tween four and five years old, with the 

 highest degree of probability in favor of the 

 smaller number. 



Francis H. Heeeick. 

 Adelbeet College. 



THE NEWARK SYSTEM. 



In an article in a recent number of Sci- 

 ence* Professor C. H. Hitchcock again ob- 

 jects to the use of ' Newark ' as a gi-oup 

 name in geology. This article is essen- 

 tially a republication of a portion of a paper 

 by the same author, which appeared in the 

 American Geologist in ISOOf in criticism of 

 an article of mine in the same journal,! 

 in which reasons were presented for reviv- 

 ing the use of Newark as a name for a cer- 

 tain system of rocks. 



I replied! to Professor Hitchcock's ob- 

 jections and criticisms, and showed conclu- 

 sively, as I believe, that the term referred 

 to has precedence over all other names ap- 

 plied to the system in question, which do 

 not imply correlation. In his recent article 

 Professor Hitchcock does not so much as 

 mention my rejoinder ; but is of the opinion 

 that the considerations presented in his ear- 

 lier paper ' would have been sufficient to 

 convince any one, looking at the subject ju- 

 dicially and impartially, of the inadequacy 



*Vol. 1, New Series, Jan. 18, 1895, pp. 74-77. 



t Vol. 5, 1890, pp. 197-202. 



i Vol. 3, 1889, pp. 178-182. 



?Am. Geo!., Vol. 7, 1891, pp. 238-241. 



