4 The American Naturalist. [January, 
ciliated canals lying between ectoderm andentoderm. They soon 
disappear. These were not carefully studied, nor were the pro- 
nephridia or head-kidneys. The permanent nephridia are regarded 
by Wilson as arising partly from the nephric rows, which are, as 
we have seen above, ectodermal in origin, and comparable in 
every early ontogenetic feature with the neural rows; the funnel 
is regarded as derived from the mesoderm proper. According to 
the account and figures, the nephric rows send upgrowths into 
every somite; these join a large cell on the anterior wall of each 
dissepiment. The large cell develops the funnel, while the cells 
of the nephric upgrowth becomes perforated to form the tubular 
portion of the nephridium. From each nephridial anlage a 
process is developed which becomes hollow, and the sete of the 
inner row are developed in the cavities thus formed. 
The speculations with which Wilson concludes his paper are 
of extreme interest, but as they deal with problems of general 
morphology they may be omitted here. 
R.S. Bergh has also studied the development of the earthworm, 
with especial reference to the nervous system and Wilson’s germ- 
bands. His account‘ differs in so many particulars that we can- 
not consider the fate of the germ-bands as settled. 
Bergh paid no attention to the segmentation and gastrulation, 
but begins his account with the formation of the germ-bands. As 
his account of the fate of the different portions differs from Wil- 
son’s interpretation, he has applied different names to different 
portions, as is seen by this schedule: : 
WILSON. BERGH. 
Primary mesoblast = Posterior myoblast. 
Neuroblast = Neuroblast. 
Nephroblasts | 
ae Licking t Anterior myoblasts. 
In the earliest stage studied by Bergh there is present on 
either side the posterior myoblast, the neuroblast, and a single 
* Bergh, R. S. Neue Beiträge zur Embryologie der Anneliden, I. Zur Entwicklung und 
des Keimstreifenssvon Lumbricus, Zeitschr. f. wiss. Zoologie, Bd. L., p. 
469, 3 pls., 1890. o 
