1901.] NATUIIAL SCIENCES OF PIIILADELPIIIA. 507 



A number of cases are known in the Anura of terrestrial ]arva3 

 with a large yolk-sphere, Avhich have been collected together in a 

 contribution by Miss L. Y. Sainjjson,^ but terrestrial development 

 in the Urodelea appears to be much less frequent. In the Ca^cilian 

 genus, IcJithyophiii, the embryology of which has been carefully 

 studied by the Sarasins/ there is a large yolk-sphere, which at first 

 becomes segmented only peripherally and not until much later 

 through its entire mass, so that here the development is at first me- 

 soblastic much as in a Sauropsidan. That may perhaps be found 

 to be the case in Plethodon also Avhen its early cleavage is studied. 

 In Ichthyophls the intestine lies at first as a straight open groove 

 upon the yolk (cf. the chapter in the Sarasins' monograph. Das 

 Schicksal des Dotters) ; then the yolk bends into a number of 

 lobes, which later become elongated and entirely covered by the 

 body wall. The intestinal groove of Ichthijophis is supposed by 

 these investigators to become a closed tube without growing round 

 the yolk- mass, but they did not have the necessary stages to show 

 the final fate of the yolk. The Sarasins laid particular stress 

 upon the peculiar development of the Civcilia in discussing their 

 relationships, as, e.g., in allying them with Amphiuma, which 

 Hay^ has shown to have quite a similar development. But the 

 fact that Amphiuma, the Cceeilia and Plethodon show great simi- 

 larity in their development, might prove rather that the formation 

 of a large yolk-mass with the embryo curled around it may be 

 merely the consequence of terrestrial development, and the simi- 

 larity express rather a case of convei'gence than of phyletic 

 affinity. The relationshi[)S of the Amphibia must be shown from 

 comparative anatomical standpoints, and not from the larval 

 development which obviously may be easily modified by change in 

 environment, as is particularly well shown in the Anura. 

 Brauer, who studied the development of the Ccecilian genus 

 Hypocjeophis from the Seychelles, where it lives wholly terrestrial, 

 concludes:* " Wenn auch kein Zweifel dariiber aufkommen kann, 



^ "Unusual Modes of Breeding and Development Among Anura," Amtri- 

 can Naturalist, 34, 1900. 



^ '' Ergebnisse naturwisseuschaftlicher Forschungen auf Ceylon,'' Wies- 

 baden, 1«87-1890. 



" Observations on Amphiuma and Its Young," American Naturalist, 



* '' Beitriige zur Kenntniss der Entwicklungsgeschichte und der Anatomie 

 der Gymnophiouen,'' Zool. Jahrh., 10, 1897. 



