MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 309 



large ganglion, viz, the uormal gangliou ceUs, in which the nucleus is surroiindeil by an abundant 

 protoplasm. 



It should also be observed that the mushroom bodies are best develojied in adult insects, and 

 especially iu those of a high degree of intelligence. Now Limulus is low in the plane of intelli- 

 gence. It burrows in the mud and iu a haj)hazard way devours whatever worms and other soft- 

 bodied animals it can obtain with its spiny-based legs. 



On the other hand we were, before reading Viallane's linal memoir, inclined to homologize the 

 "nucleogeuus bodies" of Limulus in part with the cortical masses of chromatic cells figured by 

 Saint Eemy (Figs, xii and xiii I. ol.) which envelop the optic lobes of spiders and the cerebral 

 lobes of the scorpion (Fig. xiv a. gang. m.). 



Whether a pedunculated body is present iu the brain of myriopods appears from the careful 

 researches of Saint liemy to be a matter of doubt. He does not seem to have detected auy organs 

 like them in the genera he investigated except in Julus, where he observed some vestiges which he 

 compares to the pedunculated bodies of insects. In Scutigera (Cermatia) he discovered what he 

 doubtfully homologizes with the pedunculated bodies of insects, remarking as follows : 



The homologii's of the complicated ai>paratu8 tbat we have just described are difficult — we may even say- 

 impossible — to establish with certainty. The general aspect and the disposition of the principal i>arts leads one at 

 first to think that this ens(^mble represents the pedunculated body so constant iu insects and the vestiges of which 

 we have found in Julus. But when we examine the thing more closely and push the comparison more thoroughly 

 we immediately perceive that the rcsembl.ince is absolutely superficial and that we can not find points of precise 

 resemblance between the portions of our apparatus and those of the pedunculated body of insects. We are here 

 even less well informed than in Jxilas because there are wanting the relations with the optic lobe (commissures of 

 Bellonci) which have served as in this case to affirm the existence of a rudimentary pedunculated body represented 

 by a calyx. 



From the lack of facts of this kind it nuist be acknowledged that we have to content ourselves with hypotheses, 

 though quite plausible ones. Without seeking to compare these organs in their details, we shall regard them as 

 very probably homologues. What are, indeed, the constituent parts of the pedunculated body of insects? An 

 accumulation of chromatic cells in relation with a system of medullary stalks which are planted in the proto- 

 cerebron, and end abruptly in the midst (au aein) of the punctuated substance. We shall find the same structure 

 and the same arrangements in the pedunculated organs of Scutigera. The peduncles end near the median line, as 

 does the beam (trabecula), and the internal tubercle ends near the neurilemma, as the anterior horn in these last. 

 The thin ganglionic masses seem to play, opposite these parts, the same role as the calices opposite (vis-a-vis) the 

 horn and the beam {potiire) (pp. 74, 75). 



In Peripatus also Saint Remy describes and figures a system of plates and a medullary mass 

 perhaps comparable to the pedunculated organ of Scutigera, as he states on p. 242 : 



Ce systeme des lames et de la masse m^dullaire pent etre compare :\ I'organe p^doncul^ de la Scntigfere. Ici 

 comme chez la Sciitigere, nous avons un organe m^dullaire qui recucille, d'une part, les prolongements de petites 

 cellules chromatiques pauvres en protoplasma, et est en relation, d'outre part, avec des jjieces qui s'enfoncent dans 

 la substance ponctude et se terminent franchement sans contracter de rapports .a I'extremito avec d'autres regions. 

 Mais, outre ce rapprochment fond6 cxclusivement sur des caractcres geueraus, il est possible d'en faire un autre avec 

 le corps p^doncul(S des insectes, base sur les memes caracteres et appuy<S de plus sur un fait anatomique interressant, 

 I'existence de relations eutre ces organs et le lobe olfactif, ainsi que la riSgion qui donne naissance au p6dicule 

 optique, disposition commune :\ I'organe que nous venous d'etudier chez le Pt5ripate et au corps p^doncul6 des 

 insectes. 



Under the cii-cumstances, then, we were at first unable to agree with M. Viallanes that 

 what he regards as pedunculated bodies are really such, nor did they appear to be the homologues 

 of the problematical organs in the brain of Onychophora (Peripatus), or of Myriopoda. Further 

 and very extended examination of the brain of young Limuli after their first molt, and when 

 they are less than an inch long, exclusive of the caudal .spine, are urgently needed to finally settle 

 this and other difQcult points in the homologies of the brain of Limulus. 



X. COMPARISON OF THE BRAIN OF LIMULUS WITH THAT OF ARACHNIDA. 



Thanks to the able and very detailed account and beautiful figures of Dr. Saint Remy, we 

 now have a means or standard of comparison in studying the brain of Limulus which has not 

 hitherto been aiforded us, and which have greatly aided us in coming to a better appreciation of 

 the nature of the brain of Limulus. There seems little doubt but that the brain iu question is in 

 its general features much like that of Arachnida. This is largely owing to the similarity in the 



