PUT FORTH BY VALENTIN. 223 
Pigment-globules of a black colour are soon, however, developed on 
their periphery, so that the corpuscles or vesicles just mentioned are 
transparent in their centre when they have ceased to be so, and have 
become dark on their circumference. It is plain that von Ammon and 
R. Wagner have seen this condition as well as myself. The globules 
are so small from the commencement, that they ..... This process 
of deposition of the black-coloured globules upon the pigment-cor- 
puscles goes on afterwards continuously, and to such an extent that 
the latter are enveloped and covered on all sides by them, and are only 
rendered visible when the globules are removed by pressure or wasbing.); 
and I compared the pigment-cells with the cellular tissue of 
plants. (Repertor. ii, 245. The pigment here (in the choroid) has 
the same character which it has in most other parts of the body, that 
is, a round, clear, transparent, and colourless nucleus, or the pigment- 
molecules lie closely crowded together around a pigment-vesicle. These 
heaps of pigment composed of pigment-vesicles, and the molecules of 
pigment deposited around them, are extended out sidewise, and in man, 
the dog, the rabbit, the horse, the ox, and such lke, form unequal 
pentagons or hexagons, which are placed close together in a similar 
manner to the cells of the parenchymatous cellular tissue of plants. 
Langenbeck de retina, 38.) Schwann gave an essential complete- 
ness to these analogies, by showing that the gelatinous primordial 
mass of the tissues was composed of cells, that the bodies im- 
bedded init are nuclei, and that these and the cells often exhibit 
analogous laws of development. (Froriep’s Notizen, 1838, 
Mikroskopische Untersuchungen iiber die Struktur der Thiere 
und Pflanzen, Heft 1, 1838.) As early as 1837 I had observed © 
the cells of the germinal membrane in the ovum of sepia, with 
their nuclei and nucleoli, and the areas surrounding them, and 
had communicated my researches in a letter to Breschet. Shorily 
after I became acquainted with Schwann’s first communication I 
commenced the investigation of the subject. The chief results 
of my inquiries are contained in the following communication. I 
have, at the same time, referred to the corresponding passages 
in the first part of Schwann’s treatise, which I have received 
this day.” 
I will only add that the second part also, (consisting of sheets 
8 to 18, and Plates III and IV,) therefore the whoie of the 
portion of my treatise containing the observations, had appeared 
previous to Valentin’s researches, and had been communicated to 
the Parisian Academy in the year 1838; a remark which does 
not appear altogether superfluous, since Professor Wagner has 
