NOTES ON THE EMBRYOLOGY OF LIMULUS. 
567 
none cause any serious modification of the views here held. Professor Lankester 
[’85], entirely independently, has arrived at essentially similar views as to the 
homology existing between the lungs of Arachnids and the gills of Limulus. 
The causes assigned for the change differ, a matter of no importance in this 
connection. Mr. Pelseneer [’85] has shown that the brain of Apus is a 
“ syncerebrum,” a fact which modifies some of the statements in the text. 
The discovery by Mr. Spencer that the urinary tubules of the Amphipods are 
mesenteric [’85] is more important, though I must say that my argument 
demands analogies rather than exact homologies. 
Dr. Packard [’85] has studied some sections of a stage about equal to my 
figure 5, and from them he draws the conclusion that the development of the 
brain of Limulus is entirely different from that of Arachnids. He distinctly states 
that the stage cut had the first pair of appendages in a post-oral position, but 
still he regards the nervous invagination in sections which pass through the 
first pair of limbs as the brain. This being the case, his argument falls to the 
ground. Contrary to his statements, I would say that the development of the 
brain of Limulus is closely like that of the Arachnids, and that Crustaceans 
do have procephalic lobes. 
Bibliography. 
’84. Ayres, Howard. — “On the Development of (Ecanthus niveus 
and its Parasite, Teleas,” ‘ Mem. Bost. Soc. Nat. Hist.,’ iii, pp. 225 — 
281 ; pis. xviii — xxv (1884). 
’73- Balbiani. — “ Memoire sur le developpement des Araneides,” ‘Ann.d. 
Sci. Nat.,’ v serie, t. xviii, pp. 1 — 91 ; pis. i — xv (1873). 
’80 a . Balfour, Francis Maitland. — ‘A Treatise on Comparative Em- 
bryology,’ vol. i, London (1880). 
’80 b . Balfour, Francis Maitland. — “Notes on the Development of the 
Araneina,” ‘Quart. Journ. Micr. Sci.,’ vol. xx, pp. 167 — 189; pis. 
xix — xxi (1880). 
'83. Balfour, Francis Maitland.— “ The Anatomy and Development of 
Peripatus capensis” [Edited by H. N. Moseley and Adam Sedg- 
wick], ‘Quart. Journ. Micr. Sci.,’ vol. xxiii, pp. 213 — 259; pis. 
xiii — xx (1883). 
’71. Van Beneden, Edouard. — (No title) [Position of Limulus] ‘ C. R. des 
Seances d. 1. Soc. Ent. Belg. Ann.,’ 1$71, pp. ix — xi. The same 
appeared as, “ On the Systematic Position of the King Crabs and 
Trilobites,” ‘Annals and Mag. Nat. Hist,.,’ iv, series ix, pp. 98, 99 
(1872) ; “ De la place que les Limules doivent occuper dans la classi- 
fication des Arthropodes d’apres leur developpement embryonnaire,” 
‘Journ. de Zool.,’ i, pp. 41 — 44 (1872). 
