3 , 4 DISCOVERY REPORTS 



surface; a feat which they accomplish by extruding a bubble of air through the pore of the float. In a 

 few minutes the gas regenerates and then the animals rise to the surface'. A. Agassiz (1883) had 

 already observed a young specimen of about 6 mm. 'swimming at various levels in the jar in which it 

 was kept '. Miss Eleanor Dodge, writing from Miami, has kindly informed me that she has talked with 

 people who have caught Physalia in plankton nets with their floats empty, but she did not refer to 

 their size; it looks as if they must have been small, perhaps larval stages. 



»/HAECKEL) 

 -IOO 



(HAECKEL) 



/» 



/ 



/ 

 / 

 / 

 / 



/*CQUATREFAGES) 



FLOAT- LENGTH 



(HAECKEL) 



(KISCH" 



Text-fig. 4. Physalia physalis. The relation between the diameter of the gas-gland and the length of the float. 



My companion at Lanzarote, George Mackie, made some experiments by withdrawing measured 

 quantities of air from the pneumatocyst with a hypodermic syringe, but there was little subsequent 

 change of volume. 



Quatrefages seems to have been the first to have analysed the contents of the pneumatocyst; his 

 results are given in Table 5 : 



Table 5 



Percentage of 



