312 ORR. [Vol. I. 



The species on which most of my work has been done is 

 Anolis sagrm (Dum. et Bib.), but I have also examined 

 some stages of SpJicerodactyhis notabis (Baird) and LiocepJiahis 

 carinatiis (Gray). The embryo of Anohs develops in the uterus 

 until about the stage represented in Fig. 2, C, PI. XII, I found 

 the full-sized eggs, rarely four in number, in the uterus. They 

 have a hard white shell when deposited, and could be obtained 

 in large numbers in the sand-filled crevices of heaps of broken 

 conch-shells on the sea-beach. The eggs of the other two 

 species are of a different size, with soft shells. The embryos 

 were killed in Perenyi's fluid, and preserved in 90° alcohol. 

 After this method of treatment I found a saffranin stain gave 

 the best results. 



Owing to the ventral curve in the head of the embryo (cra- 

 nial flexure), the words "anterior" and "posterior," etc., come 

 to have two meanings. One has regard to the entire embryo, 

 in which sense the extreme anterior end of the embryo 

 would be the dorsal summit of the mid-brain. The other 

 meaning regards the organs as they would appear if the 

 curve were rectified and the head continued in the straight 

 line of the body axis. In this case the extreme anterior end 

 would be the outer surface of the front median lip (anterior 

 medullary fold) of the medullary groove. This would also be 

 the dividing line between the dorsal and ventral surfaces. As 

 this latter morphological meaning expresses the homologies 

 of the parts and greatly simplifies the terminology, I shall 

 adopt it throughout. 



Except where otherwise specified, the description and figures 

 refer to Anolis. 



PART I. 



Getieral Description of Youngest Stage. 



The youngest stage which I have obtained is represented 

 entire in Fig. i, A, and in sections in Figs. ;?, A-18, A, inclusive. 

 There are four protovertebrae. The cranial flexure is well 

 marked, and the lateral medullary folds touch each other above 

 the central canal from a point just behind the primary fore- 

 brain, backward as far as the lumbar region. Although the 

 medullary folds touch each other through this distance, they are 



