FURTHER STUDIES 0\ THE RRAIN OF LIMTEUS POLYPHEMUS. WITH 

 iNUTES UN UrS EMBRYOLOGY. 



15V Ai.i'inu s S. Packard. 



TAULK OK CONTKNTS. 



Fam 



I. Introduction 289 



II. (.ienural nniitomy of the bniin of Liiunlns 290 



III. Tlio raorpliology of the brain of LiiiiuIiiH, swu oxten.ally, as compared with that of Arachnids 292 



IV. Histology.. 296 



V. The latoral-cyo ganglia or lobes 297 



VI. T\w niediau-oyo ganglia or lobes 299 



VII. The .irebral ganglia or lobes 300 



VIII. Kesult.s I'ouiparvd with those of other ol)8erver8 303 



IX. The homologies of the so-called "nncleogenous" or " pedunculated bodies" 305 



X. Comparison of the brain of Liniulus with tliat of Aracbnida 310 



XI. Notes on the embryonic dovelopmeut of the brain and nervous cord '. , 313 



XII. Observations on the development of the abdominal lege and of the branchiie 315 



XIII. liiblionraphy 323 



I. iNTKODUf'TION. 



In a former memoir I attempted to describe the brain or preopsophageal ganglion of 

 Liinulus. The section.s were made from brains di.ssocted from the living animal and .stained in 

 the manner described by Diet), being allowed to remain in the csmic acid liom twenty to 

 forty honrs, while other sections were made by my friend, Mr. Norman N. Masou, from two brains, 

 one of which had been several years in alcohol. 



Not at all satislied with my first essay, not having satisfactorily worked out the topography 

 of the (lirt'crent lobes, I have for several years past, after numerous interruptions, endeavored to 

 get a clear idea tif the mr)r])li()logy of the central nervous system both of the adult Limulus and of 

 the embryo, as well as of the freshly hatched larva. Since my first essay appeared two most valu- 

 able and exhaustive contributions to our knowledge of the Arthropod brain have been published — 

 the elaborate and riclily illustrati-d memoirs of M. II. Viallanes on the brain of the locust and 

 other insects, and the very sound, detailed, and copiously illustrated work of Dr. Saint Eemy 

 on the morphology of the brain of Jlyriopoda, Arachnida, and Peripatus. In this last work we 

 have for the lirst time a thorough and exhaustive treati.se on the brain of spiders and of the 

 scorpion, and to this work I am indebted for the means of comparison of the brain of Limulus with 

 that of the class of Arachnida. 



Several years ago my friend and colleague, Prof. H. C. Bumpus, made a series of sections of 

 the brain of the young Linnilus, when about two inches long. The .series of tran.sverse .sections 

 were stained with osmic acid and were ;^ millimeter in thickness, a .single brain being cut into 429 

 slices arranged serially; tlie brain was, as in the other .sections made by Iiim, removed from tlie 

 living animal and immediately stained and cut. A series of 102 sagittal or longitudinal .sections 

 of another brain was stained with alum, carmine, and eosin. The most vuseful sections of the young 

 animal, liowever, were tlie liori/.ontal ones, Tfi in number and ^\ millimeter in thickness, which 

 were stained with Iiaiiiatoxylin and c<»sin. 



289 

 S. Mis. lO'J 19 



