NUDIBRANCHIATA. 25 



Peach informs me that many species come inshore at 

 Wick every spring, for the purpose of spawning. Their 

 fecundity is very great. One of their functions is thus 

 fulfilled by these and 



" all kind of natures, 

 That labour on the bosom of this sphere, 

 To propagate their states." 



In a day or two after copulation the spawn is depo- 

 sited. This is enveloped in a perfectly transparent 

 mucus, which at first is tenacious and adheres to what- 

 ever it comes in contact with. While shedding the 

 spawn the animal slowly and gradually moves backward 

 in a spiral direction, beginning in the centre ; thus the 

 spawn assumes the form of a coil. The fry generally 

 emerges from its gelatinous covering in about ten days 

 or a fortnight after the spawn has been deposited. 

 " That a minute creature, scarcely visible to the naked 

 eye, enclosed in an operculated shell, and swimming 

 freely through the water by means of ciliated lobes, 

 should turn into the large and sluggish Doris tubercu- 

 lata or Tritonia Hombergii, is one of nature's romances, 

 only to be learnt by a careful study of her works ." 

 The Nudibranchs are frequently infested with parasitic 

 Entomostraca; these are most commonly buried beneath 

 the skin, but in some cases inhabit the abdominal 

 cavity, or adhere to the branchial processes and other 

 parts of the surface of the body. The mollusks of the 

 present order are widely distributed, from the arctic 

 ocean to the tropics ; a few are oceanic wanderers, and 

 crawl on the stalks and leaves of floating seaweeds. 

 " They require to be watched and drawn whilst living 

 and active, since after immersion in spirits they lose 

 both their form and colour " (Woodward) . With re- 

 spect to the urticating filaments of the Eolides, Huxley, 



VOL. v. c 



