Bennet M. Allen 83 
des Centraleanals des Hodens zwischen Mustelus und Acanthias zu beste- 
hen. Bei dieser Gattung wird er seiner ganzer Linge nach gebildet durch 
die Verwachsung der seitlich vom Segmantalgang nach vorn sich wenden- 
den Trichterblasen. Seithche Ausbuchtungen der letzteren bilden den 
basalem Theil der rete vascolosum. Bei Mustelus dagegen ist es nur der 
vorderste tiber die Hodenfalte hinaus vorgreifende Abschnitt des Central- 
canals den mann entstanden ansehen kénnte, denn nur an diesen setzen 
sich 2 (oder 3) Segmentalgiinge an. Der ganze iibrige viel langere 
Theil des Centralcanals entsteht aus den in das Stroma der Epithelfalte 
eingestiilpten Keimepithel Zellen.” 
Balfour, 78, shows that in the forms which he studied, the anterior 
end of the sex-gland only, was directly united to the mesonephros by 
means of the rete-canals. 
The condition in the lizard Platydactylus is, according to Braun, 77, 
quite similar. He considers the union to be formed in adult life by two 
or three rete-cords joining the anterior ends of mesonephros and testis; 
although he states that they are connected along the entire length of the 
testis in early stages. Hoffmann, 89, finds the union of rete-cords to be 
complete and intact along the entire length of the testis in Lacerta at the 
end of the first year. He did not study older specimens. Semon, 87, 
claims that there is a degeneration of the rete-cords at both the anterior 
and posterior ends of the sex-gland of the chick; but Janosik, go, denies 
this. 
MATERIAL AND TECHNIQUE. 
Our lakes in the vicinity of Madison abound in the little painted 
tortoise, Chrysemys marginata. The number of embryos to be gathered 
in the season is limited only by ones patience in the work of preserving 
them. I have prepared a large number of serial sections of the meso- 
nephros and sex-gland, as well as of entire embryos, comprising an un- 
broken chain of stages from gastrulation to adult life. 
As a fixative, Tellyesnitzky’s Bichromate-acetie fluid was almost ex- 
clusively used, as it gave most excellent results. Haidenhein’s iron-alum 
hematoxylin stain proved unsatisfactory for early stages of the embryos 
under 7 mm. length. For later stages than this it gave excellent results 
and was used almost exclusively. A counter-stain of Congo red was also 
employed. The sections were cut at a thickness of 7 p. 
Measurements were made of the distance between the cervical bend 
‘and the tail bend (C-7’). In the later stages the length of carapace was 
also given. 
To more clearly understand the origin of the sex-cords, it will be 
