; 252 Dr. Burnett's Reviews and Abstracts 
masses, with scarce a trace of any indication that they are double 
organs. . . . This union of the olfactory lobes, how- 
ever, 1S analogous to what occurs in the cerebral lobes of sharks 
other Plagiostome fishes, and in the optic lobes of the Lepi- 
dosiren, al, as it seems, in Menobranchus. Their fusion is a 
subject ‘of additional interest, since it tends to show that they are 
eveloped from a single em mbryonic vesicle, and not from a pair of 
vesicles. If this statement be true, then we have the olfactory 
lobes arrested in —s development, hm to the division of 
this vesicle. An analogous state of things is easily shown ina 
chick of the foutth day, where the optic lobes form a single ves- 
ue, though they subsequently become double and widely separ- 
ted from each other. In Lepidosiren, according to Owen, there 
is but one optic lobe, and that on the median line; we may 
therefore regard this last as the vesicle undivided. The fusion, 
or rather the absence of separation, of the cerebral lobes of Pla- 
giostome fishes, is undoubtedly to be explained in the same man- 
ner.’’—pp. 7 
In n speaking of the cerebral lobes, théir distinct separation here 
ticulate “divisions of animals. says : 
though frequent attempts have been made to homologize 
the renee systems of vertebrates and articulates, yet in reality 
there seems to exist no correct basis on which the alleged homol- 
ogy may rest.” 
After noticing Pe advocates of this view, and some of their 
gous with the spinal cord. : If a true homology 
existed, we ought at least to have representatives from the articu- 
lates and vertebrates, in which the identity would be obviously 
proximate, if not absolute. But as yet, there has been escribed 
no instance where the spinal cord, structurally iad is Sales 
ly and distinctly represented in the articulates, nor among verte- 
brates any true ganglionic chain with an @sophageal ring through 
which the esophagus passes.”—p, 9. 
