ON THE ZOOLOGICAL STATION AT NAPLES. 105 



the relief of pressure. The liue of least resistance is naturally the 

 ventral one, therefore the bladder expands downwards amongst the 

 abdominal viscera. If the expansion has been too great, the bladder is 

 incapable of recovery, and the fish remains in this position till it dies. 

 I have seen gurnards swim in this inverted position for several days 

 before death ensued. 



This seems to me to throw considerable light upon the bladder of 

 Dactylopterus. If, let us say, to escape from an enemy, it has to make a 

 sudden ascent and to leap out of the water, the conditions which prove 

 fatal to the gurnard are overcome by the peculiar structure and position 

 of the bladder. The only line of possible expansion is again towards the 

 abdominal viscera, but it is in this direction counterbalanced by the 

 action of the two strong muscles. 



The bladder, then, being prevented from expanding when the pressure 

 from the surrounding water is suddenly removed, the high dorsal position 

 of the secondary portion becomes of the greatest possible advantage. 



For, comparing Dactylo2)terus with Exocoetus, we find that it has not 

 got, in cross section, that deep elliptical circumference, nor is it provided 

 with small keels to aid its balance when in the air. A transverse section 

 of Dadi/loptertis at any part of the body shows an almost circular out- 

 line. Therefore the swimming-bladder, placed, as it is, right np in the 

 back, must be of the greatest service in enabling the fish to maintain a 

 proper position when in the air. 



Concluding, I would sum up therefore as follows : that Vadylojiterus, 

 although retaining its gurnard shape and habit of life, has, nevertheless, 

 taken to the air as a means of escaping from its enemies. To compensate 

 for its somewhat clumsy form, the swimming-bladder has been developed 

 in an unusually high dorsal position, and, to prevent sufl'ering fi-om a 

 sudden alteration of pressure, has been provided with two strong 

 muscles. 



IV. Report on the Occupation of the Table. By Mr. Arthur Willet. 



I had been staying at Faro, near Messina, upwards of two months, 

 from the beginning of jMay, collecting larvoe of Amphioxus ; and. after 

 having preserved a sutficient quantity up to a certain stage in the 

 development, I had to wait some weeks for the final larval stages. In 

 order to make the best use of my time, I came here on July 15, by the 

 kind permission of the British Association Committee, for the purpose of 

 examining my material and finding out the best method of conservation. 



I made preparations in tuio, and also cut sevci-al series of sections 

 ■with a ' Jung ' microtome, and in this way I found that osmic acid was 

 the best reagent for killing the larvae as it causes the least amount of 

 histological disturbance. This was obviously a most important point to 

 decide upon for my future preparations. 



I have also made use of the library for reading up the literature on the 

 subject, and have paid some attention to the fauna of the Gulf of Naples. 

 I am now returning to Messina. Although I have been at Naples such 

 a short time, less than three weeks, I consider that it has been a great 

 advantage to me to work here, and I am extremely obliged to the 

 Committee of the British Association for permitting me to use their 

 table. 



