Mr. A. S. Packard, Jun., 07i Limulus. 371 



the spine there are six segments. We venture to suggest 

 that four of these segments are purely imaginary. Embryo- 

 logy, as we have indicated in our figures, shows that there 

 are but nine segments in the abdomen of Limidus, the spine 

 forming the ninth. Our author speaks of the " postanal 

 spine," when the anus is plainly situated in the base of the 

 spine itself. It is a general law in the Arthropods that the anus 

 opens in the terminal segment of the body. There are fifteen 

 segments in the body of Ltmulus, as embryology abundantly 

 shows. In order to compare the body oi Limulus with its fifteen 

 segments or arthromeres to tliat of the scorpion with nineteen, 

 Mr. Lankester conjures up four additional segments, which 

 are pure metaphysical inventions. The cephalothoracic plate 

 or carapace is more thaii once styled a " sclerite." The 

 author here (as usual) sets aside the embryological proof that 

 the carapace is composed of the tergites of six segments, and 

 allows, apparently as the result of his own independent 

 observations (as if no one had previously proved it*), that 

 the carapace may " be considered as representing six coalesced 

 tergites." Partly on metapliysical grounds, and partly from 

 the presence of movable spines on the sides, which, however, 

 are situated on the anterior limb-bearing segments of the 

 abdomen, as well as on the seventh and eighth limbless seg- 

 ments, our author is encouraged in the belief that these four 

 hypothetical segments really exist. We prefer the plain 

 teachings of observed facts, which are capable of demonstra- 

 tion and proof, and would ask for better evidence than this 

 article affords of the existence of such segments. We would 

 also continue to regard the anal s]nne as the telson. Lan- 

 kester's " telson " is made up of the consolidated thirteenth 

 and fourteenth segments of the body plus the anal spine or 

 fifteenth (or ninth abdominal) segment. 



Our author sets out with the foregone conclusion that he 

 "must" find in the "abdominal carapace " of Z«'ww/ms the 

 representatives of the twelve abdominal segments of the 

 scorpion, and so with a method of his own he creates them 

 out of his inner consciousness. 



• In a preliminary paper on the Embryology of Limulus pohjphcmus 

 read before the Amer. Assoc. Adv. Science, Auumst 1870, and printed in 

 tlie ' American Natvu-alist ' for October 1870, which our author has appa- 

 rently not seen, the six segments of the embryo Limulus when in the 

 trilobite stage are figiu-ed, and the number of thoracic segments is stated 

 in the text. This paper is a summary of the memoir printed in the 

 'Memoirs of the Boston Society of isatural History,' and contains a 

 general account of the embryology of Limuhis, and appeared, with iigures, 

 over a year in advance of any other account of the embryology of Limulus. 



