TRANSACTIONS OF SECTION D. 709 



it another way, the Lept.oclinum is protected against enemies to some extent for Ihe 

 benefit of the Lamellarin which preys upon its vitals. 



It is, to my mind, no sufficient objection to theories of protective and warning 

 colouration that careful investigation may from time to time reveal cases where a 

 disguise is penetrated, a protection frustrated, an ofi'ensive device supposed to 

 confer inedibility apparently ignored. AVe must bear in mind that the enemies, 

 as well as their prey, are exposed to competition, are subject to natural selection, 

 are undergoing evolution ; that the pursuers and the pursued, the eaters and the 

 eaten, have been evolved together ; and that it may be of great advantage to be 

 protected from same, even if not from all enemies. Just as on land some animals 

 can browse upon thistles whose ' nemo me impune lacessit ' spines are supposed to 

 confer immunity from attack, so it is quite in accord with our ideas of evolution 

 by means of natural selection to suppose that some marine animals have evolved 

 an indifference to the noxious sponge or to the bristling Ascidian, which are able 

 by their defensive characteristics, like the thistle, to repel the majority of 

 uivaders. 



Although we can keep and study the Littoral and Laminarian animals at ease 

 in our zoological stations, it may perhaps be questioned how far we can reproduce 

 in our experimental and observational tanks the conditions of the ' Coralline ' and 

 the ' Deep-mud ' zones. One might suppose that the pressure — which we have no 

 means as yet for snpplyirg' — and which at 30 fathoms amounts to nearly 100 lbs. 

 on the square inch, and at 80 fathoms to about 240 lb., or over 2 cwt. on the 

 square inch, would be an essential factor in the life conditions of the inhabitants 

 of such depths, and yet we have kept half a dozen specimens of Calocaris 

 tnacandrea, dredged from 70 to 80 fathoms, alive at the Port Erin Biological 

 Station for several weeks ; we have had both the red and the yellow forms of 

 Sarcodictyo7i cateiuita, dredged from 30 to 40 fathoms, in a healthy condition with 

 the polypes freely expanded for an indefinite period; and Mr. Arnold "Watson 

 has kept the Polynoid worm, Panthaiis oerstedi, from the deep mud at over 

 50 fathoms, alive, healthy, and building its tube under observation, first for a 

 week at the Port Erin Station, and then for many months at Sheffield in a 

 comparatively small tank with no depth of water. Consequently it seems clear 

 that, with ordinary care, almost any marine animals from such depths as are 

 found within the British area may be Icept under observation and submitted to 

 experiment in healthy and fairly natural conditions. The Biological Station, with 

 its tanks, is in fact an arrangement whereby w^e bring a portion of the sea with its 

 rocks and bottom deposits and seaweeds, with ifs inhabitants and their associates, 

 their food and their enemies, and place it for continuous study on our laboratory 

 table. It enables us to carry on the bionomical investigations to which we look 

 for information as to the methods and progress of evolution; in it lie centred our 

 hopes of a comparative physiology of the invertebrates — a physiology not wholly 

 medical — and finally to the Biological Station we confidently look for help in 

 connection with our coast fisheries. This brings me to the last subject which I 

 shall touch upon, a subject closely related both to Oceanography and Bionomics, 

 and one which depends much for its future advance upon our Biological Stations— 

 that is the subject of 



AQTTlCtrLTUEE, 



or industrial Ichthyology, the scientific treatment of fishery investigations, a 

 subject to which Professor M'Intosh has first in this country directed the 

 attention of zoologists, and in which he has been guiding us for the last decade by 

 his admirable researches. What chemistry is to the aniline, the alkali, and some 

 other manufactures, marine zoology is to our fishing industries. 



' Following up M. Regnard's experiments, some mechanical arrangement 

 whereby water could be kept circulating and aerated under pressure in closed tanks 

 might be devised, and ouglit to be tried at some zoological station. I learn from 

 the Director at the Plymouth Station that some of the animals from deep water, 

 such as Polyzoa, do not expand in their tanks. 



