48 PROGRESS or MICROSCOPICAL SCIENCE. [The Monthly Microscopical 
L Journal, JanuRry ij 1869. 
he describes " free cells " in the blastoderm, which are indepen- 
dent of the former. The cell-mass, which spreads out from the 
" germinal pole," as germinal membrane, completely surrounding the 
yolk, has been described by Von Baer, Vogt, and others, as forming 
an incomplete closure, the latter being looked upon as the anus. 
He has never observed this "primordial anus." He holds, with 
Lereboullet, that the formation of the embryo begins from the margin 
of the germinal membrane, the most peripheral part of which he 
describes as a sharply-defined zone of peculiar cells, not to be con- 
founded with a mere swelling. He applies to it the term ^^Saum,'' 
" Keimsaum," germinal fold, part of which he describes as " em- 
bryonic shield," which is identical with Vogt's " primitive band " and 
LerebouUet's "embryonic band." Arising from the germinal shield, 
he describes the " primitive line or trace," extending into the yolk, 
and the shield undergoing at the same time a process of depression, 
presenting the appearance called by Von Baer the " dorsal furrow," 
but, unlike Von Baer, Vogt, and Lereboullet, he has not been able to 
observe the formation of a bridge over the dorsal furrow. The forma- 
tion of two vesicles is then mentioned as the next advance in the pro- 
cess of development, one at the free extremity of the (Kiel) primitive 
trace, considered to be the urinary bladder or allantois, the other the 
pericardium. Previous investigators overlooked the early formation 
of these two vesicles, but Kupfifer says, " These structures appear so 
early, that I may definitely assert that the two vesicles, of which I 
maintain the anterior to be the commencement of the pericardium, and 
the posterior the allantois, are the first organs in the embryonic shield 
which can be observed." Many new facts are referred to, in regard to 
the development of these ova, such as the appearance of two, and not 
three, divisions of the brain- section, that the splitting of the germinal 
membrane into layers proceeds from the middle-line of the shield, the 
development of the eyes between the two upper layers, and the entire 
detachment of the horny layer from the upper central line, and the 
formation of a furrow beneath this layer, raised as epidermis, which 
(the furrow) penetrates into the chorda dorsalis from above. The 
author's observations on the way in which the vascular system is 
formed are incomplete. On this head he says himself " that he has 
only definitely proved the formation of blood-corpuscles in the wall of 
the yolk-bag." 
The 3Iorp}iology of the Hair. — In a long and interesting paper by 
Dr. A. Goette, of Tiibingen, the author describes the mode of growth 
of hair, and its varieties, the number of which he increases by the 
Schalthaare, " hairs of insertion." The development of the hairs of 
the embryo, as they are observed about the mouth and the eyes, he 
describes as follows : — " The first impulse to the formation of a hair is 
given by a limited cell-proliferation of the cutis, immediately beneath 
the epidermis. This cell-proliferation raises the latter into a small 
eminence, which appears to the unaided eye as a white dot. Whilst 
the closely-packed cells of the cuticular papilla separate towards the 
connective tissue into a round corpuscle, it is from above surrounded 
by the mucous stratum of the epidermis, and by continuous growth 
