of Edinburgh, Session 1885 — 86 . 
815 
Starting from one of the most defensible set of terms — that used by 
Voigt after Semper — with the four or five stages of (1) sex-cells, 
(2) spermatogonia, (3) spermatocytes, (4) spermatides or immature 
(5) spermatozoa, it will he convenient in the citation and comparison 
of observations by different authorities to distinguish the different 
stages by the following simple notation : — (1) The spermatozoon, 
denoted by S ; (2) the immature sperm or the spermatide, by S° ; 
(3) the spermatocyte, by SS ; (4) the cell which gives rise to the 
spermatocytes, or the spermatogonium, by S 1 ; (5) its antecedent, 
by S 2 ; and so on. These symbols can be readily bracketed after 
the terms cited, and all confusion thus obviated without new or 
dogmatic nomenclature. 
§ 3. Since equally competent observers give most divergent accounts 
of the nature of spermatogenesis, it seems all but impossible that 
any one mode of development prevails. A forcible reconciliation 
may indeed be attempted by a detailed criticism of the observations, 
by pointing out, as Biondi has lately attempted, how the different 
phenomena described may occur as the various phases of one 
developmental cycle. The discrepancies are, however, too great for 
any such general mode of reconciliation. Unless we attach con- 
siderably greater weight to the observations of at least a majority 
of all the above workers than they sometimes incline to grant 
to those of each other, the literature and iconography of histo- 
logy become of little worth. Accepting the results of competent 
authorities, it is our object in this paper to propose a possible 
rationale of the existence of several different modes of develop- 
ment, and a consistent method for their classification and com- 
parison. 
In 1847 Reichert pointed out the homology between the ovum 
and the mother sperm cell, and this has been for long recognised 
with more or less definiteness in the various attempts which have 
been made to draw parallels between the processes in the develop- 
ment of the two elements. Thus Von la Valette St George compared 
spermatogonium (S 1 ) with ovum, and the follicular skin of the 
former with the follicular cells of the latter. jSTussbaum, following 
La Valette, has in his well-known memoir on the differentiation of 
sex, drawn a similar more extended parallel, and has maintained that 
in Amphibia and Teleostei the spermatogonium and its follicular 
