388 MORRIS M. WELLS 



Among the invertebrate forms, the limpets are particularly 

 interesting in connection with investigations of the homing 

 instinct. These animals possess none but the simpler types of 

 sense organs yet show marked ability in finding their way back, 

 at regular intervals, to a given resting place or " home." The 

 observations herein recorded possess only passing biological 

 interest when taken singly but it is felt that as a whole they 

 may be of some assistance to other observers who are interested 

 in limpets and their homing behavior. They were made, during 

 the winter of 1915, at which time the author was staying at 

 the Scripps Institution for Biological Research, which institu- 

 tion is located at Lajolla, California. 



PRESENTATION OF DATA 



The rocks, on the beach to the north of the Scripps labora- 

 tory, are thickly populated with limpets belonging to three 

 genera and to at least six species. The genus Acmea is repre- 

 sented by the species patina, persona, scabra, and spectrum. 

 The two other genera are Lottia and Fisurella; of these genera 

 one species each is common, namely, L. gigantea and F. volcano. 



1. Distribution of the limpets. — The limpets show marked 

 generic and specific differences in their distribution on the 

 beach. The most common species is Acmea scabra, which occurs 

 in great numbers on all the rocks of the high and middle beach. 

 The other species of Acmea are not so numerous nor so widely 

 distributed as scabra. A. patina and A. persona are found with 

 scabra on the middle beach while A. spectrum is usually more 

 abundant on the lower beach. Lottia gigantea occurs only in 

 situations exposed to the main force of the waves. Specimens 

 of Fisurella volcano were frequently collected from the kelp- 

 covered rocks that are barely exposed at low tide. A large 

 per cent of such specimens were living in the hollow halves of 

 the deserted bivalve shells that are firmly cemented to these 

 rocks. 



2. General behavior of the limpets. — The movements of the 

 limpets are largely controlled by the tides. When the tide is 

 out, they remain practically motionless on the rocks and present 

 no visible sign of life. With the first dash of spray from the 

 incoming tide they begin to move and are apparently active 

 until the water recedes once more. 



