390 proceedings of the academy of [1893. 



land mollusca,but singly or few aggregated. They are at first not 

 globular, but distinctly ellipsoidal, the shell being perfectly glassy 

 and transparent, so that yolk division and the formation and devel- 

 opment of the embryo may be observed through it. 



The buccal body and radula develop rather rapidly. In an 

 embryo taken from the ovum, about 2-5 mm. long when extended, 

 not quite mature, with the caudal bladder still rather large, but the 

 heart formed and regularly contracting, the shell measured about 0-35 

 mm. long. The radula was 0-35 mm. long and had as many as 34 

 transverse rows of teeth. In the first of them there were 3 teeth, the 

 central and a lateral on either side, appearing as thin, barely visible 

 plates, or mere traces (O 3 , in fig. 1). Other specimens showed the 

 same more distinct, as represented in fig. VI. In the following 

 transverse rows they are larger, and rapidly develop in shape, while 

 at the margin new teeth of the same character are added, at first 

 with each row, then at greater and greater intervals, so that, in the 

 radula mentioned above, the formula was 12-C-12 in the twenty- 

 fifth transverse row. The development of the radula proceeds com- 

 paratively very fast, in this and other species, faster than the growth 

 of the animal, so that even very young specimens have the radula 

 far advanced and show nothing more of the earliest formed teeth. 

 The addition of new teeth is not always regular and symmetrical on 

 both sides ; thus, the fifth longitudinal row may begin at the sixth 

 transverse row on one side, and with the seventh on the other, so 

 that the formula for the sixth would then be 5*c*4. 



Not all of the teeth are formed and transformed in the same way, 

 in this and other species, as may be seen by the figures. But Limax 

 campestris, and other Limaco- Zonitidce and Helicidce, show such new 

 and unexpected features that they must be considered more in 

 detail. 



For a better understanding and easier reference the following table 

 gives the particulars of a series of the specimens examined, all of 

 them, except two, being represented in figs. I-V on PL 10. 



Enibryo 2'0 mm. long ; radula 0'3 mm. long, with 27 transverse rows. 



Fig. 1. Embryo 2'5 mm. long ; radula 0'35 mm. long, with 34 transverse rows. 



Animal 3'0 mm. long ; radula 0'55 mm. long, with 56 transverse rows. 



Fig. 2. Animal 3'5 mm. long ; radula 0'72 mm. long, with 65 transverse rows. 



Fig. 3. Animal 7 mm. long ; radula 1'15 mm. long, with 86 transverse rows. 



Fig. 4. Animal 15 mm. long ; radula 2'24 mm. long, with 104 transverse rows. 



Fig. 5. Animal 27 mm. long ; radula 2'72 mm. long, with 105 transverse rows. 



3 They were first overlooked, and afterward designated as O in the original 

 drawing, of which the present is a copy. 



