456 LESLIE B. AREY AND W. J. CROZIER 
remain it would add decidedly to the creature's homochromicity/ 
it is important to note that the powerful repugnatorial mantle- 
glands are found developed to an equal degree in Onchidia of 
whatever variety of pigmentation. Bret nail ('19) states that 
O. damelii and O. chameleon exhibit ''the chameleon-like prop- 
erty of changing their colors, especially when disturbed" or 
placed upon a different background. No basis for such color 
modification is known, nor is one described by Bretnall; nothing 
of this sort occurs in 0. floridanum. 
These facts are incompatible with the notion that the colora- 
tion of Onchidium involves adaptive restraint. Some reasons 
have been given (Crozier and Ai'ey, '19 a) for regarding the color- 
ation of an Onchidium as the result of genetic factors primarily. 
It is therefore noteworthy that the breeding habits of this snail 
may provide a mechanism for the perpetuation of a racial type, 
lightly pigmented, which probably would behave as a recessive 
in crosses with dark-hued forms. Onchidia are 'simultaneous' 
hermaphrodites, exhibiting reciprocal insemination (cf. also 
Joyeux-Laffuie, '82). Joyeux-Laffuie states that 0. celticum 
conjugates during its periods of emergence upon the rock. We 
have never seen this in 0. floridanum, and believe that copula- 
tion occurs within the nests. Even if it should occur in the 
open, however, each colony is in large measure prevented by its 
habits from mmgling with the members of other communities, 
so that an appreciable degree of inbreeding may safely be pos- 
tulated. Eggs are deposited during July within the nests, 
attached in pearly masses to the upper surfaces of the rock 
cavities, and the creature which emerges from the egg membrane 
has already the form of an adult. 
The intimate physiology of the peripheral glands, referred to 
as 'repugnatorial glands,' will be considered in a subsequent 
paper.. It is pertinent, however, to mention here some observa- 
tions upon their use in nature. 
Semper ('81) regarded the glands as of service in warding off 
the attacks of certain intertidal fishes. According to Semper, 
* It may be pointed out that the non-removal of the slime coating of the 
snail's back might interfere with dermal respiration. 
