81 
wall (Fig. 1). Further back the plate narrows (Fig. 2) to a thick 
band that lies on a bridge of tissue between the great cardinal vein 
and the mesonephros; still further back the band becomes grooved ; 
and again after a considerable number of sections we find the groove 
closing over to form a tube. 
Rs. Fig. 2. 
Ao. Aorta. A, C. Alimentary canal. Br. Bronchus. C. V. Cardinal vein. D. Diver- 
tieulum of coelom. Gl. Glomus. M&M. d. Miillerian duct or its Anlage. Mes. Mesonephros. 
Fig. 1. Section through a Crocodile 12 mm in length. 
Fig. 2. Section of same further towards the posterior end. 
It is noteworthy that where the plate narrows to a band, and 
becomes grooved, there is an involution of the epithelium (Fig. 3) 
just external to it; and as this becomes deeper further back, the 
Müllerian duct Anlage with the subjacent part of the body wall is 
practically severed from its original lateral connection, and remains 
attached only dorsally and on the inner side, where the mesonephros 
is fused with the detached part of the lateral body-wall (Fig. 4). 
For a considerable number of sections the mesonephros and the part 
of the body-wall bearing the Müllerian duct Anlage are readily 
distinguished; but where the grooved Anlage becomes a tube, the 
associated part of the body-wall is almost lost, and the Miillerian 
duct Anlage appears lying immediately on the mesonephros, or 
separated from the mesonephros and connected with the dorsal body- 
wall only by a very slight layer of parietal mesoblast. 
The next specimen (C) that I have to describe was of unknown 
