No. 2.] EMBRYOLOGY OF THE AMERICAN ALLIGATOR. 201 



agilis, 1882-84. Strahl's Fig. 1 (23) agrees with Fig. 12 of 

 the alligator : the structure in the successive figures of Lacerta 

 up to Fig. 7 are so similar to the corresponding stages of the 

 alligator as to call for no special remark. In Strahl's Fig. 7, 

 which is of the ventral surface, there is a median process just 

 behind the head-fold, and unfortunately it is unlettered ; it is 

 similar in appearance to the thick median area on the ventral 

 side of the head-fold in the alligator, or it might be the second- 

 ary fold on the dorsal surface of the head-fold showing through. 

 Of Strahl's remaining figures, only 1, 2, and 3 (28) differ from 

 the alligator. In these three there are shown very prominent 

 wing-like sacs, one on either side of the mid-line, near the ante- 

 rior end, which are described as the areas where the mesoderm 

 has split. 



There are five pharyngeal clefts in the alligator, which agrees 

 with the number in the Lacertilia as reported by Born 1 for 

 Lacerta and Anguis, by Hoffmann (10) for Lacerta, Van Bem- 

 melen for Lacerta, and Orr (16) for Anolis sagrczi. 



One finds the first four clefts open in Anolis ; in the alligator 

 I have never found but the first three open. Hoffmann 2 found 

 only the second cleft open in one of the Ophidia, Tropidonotus 

 natrix. 



The connection between the first, second, and third clefts 

 occurs also in the Lacertilia ; it can be seen in Fig. 2 C, PI. XII, 

 of Orr's paper referred to above, which represents an embryo of 

 Anolis sasrrceL So far as I am aware, this connection between 

 the pharyngeal clefts has not been mentioned before, and I do 

 not know of any figures which show it, other than Orr's and my 

 own. 



In Orr's figure the outlines of the connection from the first 

 to the second cleft are stronger than is the outline of the lower 

 or ventral part of the first cleft, and the ventral line of the con- 

 necting groove is carried across the first cleft to its anterior 

 border. 



Looking to the embryology of the Chelonia, one finds the 

 earlier stages figured by Agassiz (1) and by Mitsukuri and 

 Ishikawa (15). Figs. 1 to 4, PL XI, of Agassiz I cannot har- 

 monize with those of Mitsukuri, nor with mine of the alligator ; 



1 Born, Zool. Anzieger, Bd. VI, s. 537, 1SS3; and Archiv fiir Mikrosk. Anal., 

 Bd. XXII, s. 271, 18S3. 2 I.e., p. 198. 



