MKMOIUS OF THE NATIONAL ACADEMY OF SCIENCES. 305 



As we bavi' ahciuly stilted M. Viallaiies' classilioatioii nf tlio regions of the Ciustiicean and 

 insect brain into three ie;rions, vi/, pioto.deuto.and tritoeerel)rnin, does not apply to thatof Liniiihis. 

 Ill my pieniiuiinary paper 1 pointed ont tliat no deiitocerehrnni r)r tritoeeiehinni is represented in 

 the hrain of Liniuhis. and it is to be observed th:it Viallanes regards the brain as composed oftwo 

 pairs ol'f;anf;lia. the lirst beinj; the piotoeerebrum, wliiU' as to the second he is (ioiil)trnl. and pro- 

 visionally calls it the *• cerveau posterieur." \'ialhines " proto<erebruni" is what we re';ard as the 

 brain i)roper, and consists orifiinally of three pairs of nenromeres, beconiinfj; respectively the ocellar 

 or nieilianeye ganjilia, the lateral-eye panjrlia, and the <erebral fj^anfrlia. 



What N'ialianes regards us the posterior brain, and as to the homologies of which he expresses 

 himself as in donbt, we rcfjard as a part of the oesophajceal ring, and as jiostcerebral. This pos- 

 terior brain j;ives rise to the cheliceral nerves. The " (Jommissiire transverse preoesophagienne" 

 1 have detected since Viallanes has called attention to it. 



Throwing out then, N'ialianes cerrcaii postMeiir,* as not forming a part of the genuine, brain of 

 Limulus, we will return to the brain proper, or prestoniial mass, viz, the protocerebrum of Viallanes, 



IX.— Till-; HOMOLOGIES OF THE SO-CALLED " NUCLEOGENOUS " OR "PEDUNCULATED BODIES." 



M. Viallanes describes at some length the structure of the series of plates which we originally! 

 called collectively the •' nueleogenous bodies, " and the nature and homologies of whicdi seemed to 

 us problematical. lie remarks: -'To eacii of the protocerebral lobes is annexed an organ which, by 

 reason of its anatomical relations and its histological structure, should be assimilated to the 

 l)edunculated body of insects. The pedunculated body of Limulus has an arborescent form. The 

 lower extremity of its stalk penetrates into the corresponding jirotocerebral lobe, its upper 

 extremity is divided dichotomouslx, into a great number of branches. These last, which end in 

 truncated extrenuties, are entirely covered by a thick (lortex of small cells very deficient in i)roto- 

 plasm, very deeply colored by stains, emitting very fine fibriljie, in a word rigorously similar to 

 the elements which form the cellular vestiture of the pedunculated body of insects." 



Tho podtinculatod body att.iins in the Limulus an extraordinary development greater than any other Arthropod 

 known, because it by itself alone forms certainly at least ,',?„ of the total mass of tlie brain. This fact is all tho 

 more remarkable since up to the present time and not without important reason it has been agreed to consider the 

 development of the pedunculated body as correlated to that of the mental faculties (jip. 3-3). 



For years the true relations of these masses or plates which I have called the '• nueleogenous 

 bodies" have been a great puzzle to me; they are so numerous and form so large a proportion of 

 the brain; but after an examination of the figures in Viallanes final work I am led to accept his 

 interpetation of these bodies, which he appears to regard as "annexed" to the cerebral lobes. A 

 re-examination of my sections and of my fitrures, which, however, do not show so clearly as his 

 PI. X, Fig. 18, the entire .stalk of the body, or its intimate connection at its ba.se with the cerebral 

 lobes, leads me to adojit Viallanes view. At tlie same time there is a remarkable difference observ- 

 able between these mushroom or i)edunculated bodies and those of insect:? and spiders, a difference 

 to which Viallanes does not refer. This .stalk, however, is in part seen in the sections represented 

 by my I'l. xiv. Fig. 18, st. m. b., where the stalk is seen to ari.se from the bulbous or lateral jjortion 

 of (he cerebral lobes {b. e. I.), and to .send off an a.scending branch, and lateral branches. In PI. 

 XX XIV, the artotype from a microi)hotograph of the same section faintly represents the cerebral 

 lobe.s, and the stalk of the miisliroom body arising from the lateral or bulbous portion. 



We will fir.st (1) consider their resemblance to the mushroom or i)edunculated bodies of 

 insects; (2) their resemblance to or lack of resemblance or homology with tin" stratified body of 

 the Arachnid brain; (.3) their absence, /. e., the unbranched and simple condition of the paired 

 cerebral lobes or ganglia in the freshly hatched Limulus larva. 



The nnishroom bodies of Dujardin; the two musjiroom bodies, with their .stem.s, of Newton, 

 or the pedun<;ulated bodies of Viallanes, and which I have, after Dujardin, called collectively the 



• In his last |>aper Viullunes regards this as the deutocerebnim. 



t Farther studies on tho brain of Limulux puhiphemus. Zool. Anzeiger, 20 April, X891. That the cheliceral 

 iierv.s are correctly named is doubtful. The so-cailed tlicliccra or first pair of appeudijges of Limulus may lie 

 found to correspond to the antenna- or rirst pair of apjiendages of the spider discovA-ed by Jarowosky. 

 S. Mis. I(i9 20 



