1909.] NATURAL SCIENCES OF PHILADELPHIA. 309 



Locy (1886) figured and described two rather late stages, in the earlier 

 of which "the lungs appear as oblong plates of cells, the large oval 

 nuclei of which are arranged in parallel rows"; ultimately there result 

 bicellular interlamellar pillars. Schimkewitsch (1887) described briefly 

 a single rather late stage before hatching, the single figure of which 

 given by him by no means proves that "the lungs of the embryo of 

 Lycosa saccata consist of true trachea? disposed in bundles." Morin 

 (1887) found the lungs to be formed from thickenings at the bases of the 

 appendages of the second abdominal segment, these thickenings becom- 

 ing the opercula, What Bruce (1887) has described as a pulmonary 

 operculum and lung cavity seems to be nothing more, and Kishinouye 

 has previously made the criticism, judging from his figs. LXXIX and 

 LXXIX, 1 than the caudal lobe at the stage of reversion and the space 

 between it and the body wall; his account has accordingly no value. 

 Kishinouye (1890) found "in the basal part of the first abdominal 

 appendage of each side, there arises an ectodermic invagination whose 

 opening faces away from the median line. ... Of the wall of the 

 invaginated pocket, that which faces the distal end of the appendage 

 is much thicker than the opposite wall, filling the interior of the 

 appendage. The cells composing it become after awhile arranged in 

 parallel rows. Each two of these parallel rows adhering together 

 produce the lamellae of the lung-book. The external epithelium of the 

 appendage which covers these lamellae becomes the operculum of the 

 lung-book after it is depressed in height." Simmons (1894) has given 

 the fullest account up to his time, and the one most fully illustrated by 

 figures. He described fully the method of invagination of the first 

 abdominal appendage, found on its inner (mesial) surface a series of 

 folds during this process of invagination, which folds he believed 

 become the pulmonary lamellae. There is, however, a great hiatus 

 between the stages of his figs. 6 and 7, and the early embryonic folds 

 do not lie in the same position as the adult lamellae. Purcell (1895) 

 found that "the earliest lung-leaves appear on the exposed posterior 

 sides of the appendages before the latter have commenced to sink 

 below the surface into the body, and completely outside of the basal 

 sack," and, like Simmons, he concludes these become the adult lamellae, 

 but without tracing completely their later history. Wallstabe (1908) 

 says he can corroborate Simmon's results, but does not enter into 

 details. 



Jaworowski(1894) presented a full account, well illustrated, but did 

 not describe any stage earlier than one considerably later than reversion. 

 He began with a stage where beneath the first abdominal appendage 



