34 Observations on the Terrestrial 



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An anatomical examination of individuals of this species, col- 

 lected on the 12tli of September, revealed the fact that it was 

 ovoviviparous ; but owing to the minuteness of the object, the con- 

 stant difficulty in dissecting these animals whose organs are so 

 interwoven, together with the extreme tenuity of its tissues, and 

 my inexperience in operating, I am unable to present more than 

 a general sketch of its anatomy. What ia given however, I veri- 

 fied by the dissection of numerous individuals, and its ovovivipa- 

 rous character is placed beyond doubt. 



The ovary, which in those species of terrestrial mollusks ex- 

 amined by Dr. Leidy, were semi-elliptic and slightly curved, in 

 this species is a globular, mulberry shaped mass, intimately adher- 

 ing to the summit of the oviduct, {Plate 1, Fig. 4,) each spheri- 

 cal lobe of the ovary, being composed of minute cells. The 

 oviduct being distended with the embryos did not present that 

 sacculated appearance described by Dr. Leidy in other species. 

 The surface of the oviduct was marked by numerous minute and 

 irregular black lines. 



Of more than twenty specimens examined, all contained em- 

 bryos in various stages of development, none contained more 

 than four embryos, while many contained but two. The eggs 

 appeared to be nearly all of the same size ; in the one nearest the 

 ovary the embryo was very active, and by means of cilia moved 

 back and forth in its envelope ; it seemed to be composed of a disk 

 surmounted by a mass of aggregated cells, no trace of a shell 

 being visible. In the next embryo the shell (composed of nearly 

 one whorl) was completely formed, showing the lines of accretion 

 distinctly, the mass of larger cells being enclosed by the shell, 

 and showing through in the region of the pulmonary cavity. 

 In this embryo I found the sub-cesophageal ganglia, with the audi- 

 tory vesicles, {Plate 1, Fig. 8,) confirming what has hitherto 

 been stated regarding the embryological development of the Pneu- 

 mobranchiata, that these are first formed of the internal organs ; 

 they difier greatly in form from the same ganglia in the adult. {PI. 

 1, Fig. 5.) I found no traces of commissures or branches in this. 

 The otoconites {PI. 1, Fig. 9,) were generally oval in shape, num- 

 bering from fourteen to seventeen in each capsule. A most sin- 



