304 SUMMARY OF CURRENT RESEARCHES RELATING TO 
mammary glands is seen as a linear epithelial thickening on each side 
of the body — a thickening strangely suggestive of the epithelial rudiment 
of the lateral branch of the Vagus-nerve in aquatic Vertebrate embryos. 
This “ milk-line ” stretches from the anterior to the posterior limb- 
rudiment, and at intervals there are swellings which generally cor- 
respond in number to the mammae which are afterwards developed. 
The Shell of a Hen’s Egg.*— Herr W. v. Nathusius has made some 
new observations on this familiar buc puzzling structure. He is firm 
in his previously expressed conviction that the egg-envelopes must be 
regarded as “ a growing organism.” Even the superficial external 
membrane is represented in the immature ovum. The rudiments are 
ovarian, the growth is by intussusception ; the theory of mechanical 
apposition of oviducal secretions is false. 
Cellular Islets at the Margin of the Blastoderm of the Chick.t 
Dr. 0. van der Stricht notes the exceptional occurrence of cellular islets 
in the vitellus beneath the ectoderm. From the first they are formed 
of distinct cells, and not of a protoplasmic mass with multiple nuclei. 
Several, if not all of them, owe their origin to a budding of ectoderm 
cells. The author cannot regard them as rudimentary vascular islets, 
which was Vialleton’s interpretation of these or somewhat similar struc- 
tures ; but their import remains unknown. 
Development of the Vertebral Column.}— Herr 0. Hasse thinks 
that the ancestral Craniota must have had a cuticula chordas formed 
from the notochord and a cuticula sceleti formed from the skeletogenous 
layer. The Cyclostomata seem, as regards vertebral column, to be 
nearest the primitive form, and the “ Tectobranchii ” (viz. Ganoids, 
Teleosteans, Anura, Amniota) retain a more primitive condition than the 
“ Elasmobranchii ” (viz. Elasmobranchs in the ordinary sense, Dipnoi, 
and Urodela). The former have at first a cuticula sceleti directly ex- 
terior to the cuticula chordas ; the latter have between the two cuticulse 
an intercuticular layer. We hardly think that Herr Hasse is warranted 
in his new use of the term Elasmobranch. 
Development of Liver and Pancreas in Trout.§ — Dr. Ph. Stohr 
finds that in Teleosteans, as also in Amphibians, Birds, and Mammals, 
the pancreas has a threefold rudiment. Even before the closure of the 
gut there appears a dorsal solid knob— the dorsal part of the pancreas; 
subsequently, on each side of the opening of the duct of the liver, there 
appears a short cylindrical body. Each of these is a pancreas-rudiment. 
The duct of the dorsal rudiment disappears ; the dorsal rudiment unites 
with the rudiment which lies ventrally to the right ; the left rudiment 
remains small ; the two ventral ducts unite and open into the gut inde- 
pendently of and behind the duct of the liver. 
Duration of Motion of Human Spermatozoa. || — Mr. G. A. Piersoll 
cites various authorities who state that the spermatozoa may continue to 
move during 24-84 hours after death, in the fluids of the seminal tract. 
Outside the body, movement has been observed by Hofmann after 
* Zeitschr. f. wiss. Zool., lv. (1893) pp. 576-84 (4 figs.). 
t Anat. Anzeig., viii. (1893) pp. 266-71 (5 figs.). 
X Tom. cit., pp. 288-9. § Tom. cit., pp. 205-8. f[ Tom. cit., pp. 299-301. 
