No. 3. — Observations on the Development of Agelena nevia. — 
By Wm. A. Locy.* 
SEVERAL memoirs have been published on the development of the 
Araneina, but the results attained are still unsatisfactory on account of 
the disagreement of authorities, and the limited extent to which the 
method of sectioning has been employed in studying the subject. Up to 
the present time only a single memoir, illustrated by figures of actual 
sections, has appeared. 
Valuable as were the works of the earlier writers, Herold (’24), Rathke 
(42), and Von Wittich (45 and 49), they now are principally of his- 
torical importance, since their labors were performed either before the 
announcement of the cell theory, or before it had gained general recog- 
nition, and before embryology had attained its pre-eminence among mor- 
phological studies. 
Claparéde (62) made extended observations on the external features 
of development, but did not discuss the preblastodermic period nor the 
period of the revolution of the embryo. 
Salensky (’71) published in Russian a memoir, the figures illustrating 
which show critical observations on the external features of development. 
He was the first to figure the “rudimentary terga ” of the period of revo- 
lution, and also the development of the procephalic lobes. 
In a short paper on the development of Pholeus, Emerton (’72) con- 
fines his observations to the external features of development. He figures 
the polygonal areas of the blastema, and erroneously concludes that they 
are blastodermic cells without distinct nuclei. The relation of the primi- 
tive cumulus to the ventral plate is well figured. 
Balbiani (’73) has produced one of the most satisfactory memoirs yet 
written ; he figures and describes in detail the external features of the 
early stages of development up to the period of the formation of the 
appendages. 
Ludwig’s (’76) observations were confined to the formation of the blas- 
toderm, and are at variance with Balbiani’s, mainly in denying the exist- 
* Contributions from the Embryological Laboratory of the Museum of Com- 
parative Zodlogy at Harvard College, under the direction of E. L. Mark. No. VIII. 
VOL. XII.— NO. 3. 
