16 CALIFORNIA ACADEMY OF SCIENCES. 



Thus, all the Liinacoid species agree in absence of exter- 

 nal shell, and therefore, while without that slight protec- 

 tion, can better escape their enemies, as Avell as the effect 

 of droughts, fires, and cold, by crawling into fissures thafc 

 the others cannot enter. They also suffer less by being 

 washed down in the winter torrents, and follow retreating 

 moisture as the streams dry up; so that some of Nos. 1, 4, 

 5, 6, 7, 8, 9, 10 may be found active all summer in damp 

 canons or spring-heads, along weedy brooks and edges of 

 ponds. Near the bay Nos. 6, 7, 8 are, however, scarce after 

 April, and Nos. 9, 10 after June. 

 Limax [AmaUa) hewstoni J- G- C. (No. 3.) 



There seems reason to believe that this species is of only 

 annual existence, which may be the case also with the other 

 Limaces, though I have not seen it published. They dis- 

 appear with the first hot, dry weather, and are then found 

 for a while in the burrows of animals a foot or two deep, 

 where their eggs are deposited (also near the surface about 

 wells and cisterns), but after July none can be found even 

 in excavations five or six feet deep. After the ground is 

 well soaked with rain in late autumn they reappear in num- 

 bers, but very few more than half grown, some of late 

 broods, perhaps surviving in the wettest spots. As none 

 are ever found far from gardens, they are absent where the 

 native species survive in the dry season. 



The variability in color among these shell-less mollusca 

 is well known, but its origin in the principle of self-pro- 

 tection by mimetic accommodation has not been much re- 

 marked upon. In this species, and some others which feed 

 chiefly at night and in cloudy wet weather, the blackish 

 tints chiefly prevail, and seem to deepen after they first 

 come to the surface, but specimens of L. campestris and 

 L. agrestis are often found of light shades or with streaks re- 

 sembling the nervations of dead leaves, among which they 

 creep in the daytime. 



In the large kinds of Ariolimax, Nos. 4 and 5, yellowish 



