MATERIAL AND METHODS 3°7 



on the peduncle of its predecessor, they gradually appear changed in character from the long feeding 

 polyps (gastrozooids) to smaller protective palpons. The gastrozooids differ from those of related 

 species in becoming separated from their tentacles. Each stinging tentacle itself is borne on an 

 enlarged base (ampulla), which supplies stinging-cells (nematoblasts) to the long stinging tentacle. 

 The palpons protect the even smaller, reduced, sexual medusoids or gonophores, which are the true 

 adults. Probably the palpons have an anal function as well. There are intermediate stages between 

 the first and last kinds of polyps. 



The float is at first relatively small (PI. VII), occupying the aboral end of the animal, but later on, 

 greatly enlarged the float appears on top. On the inner wall of the air-sac of the float is a round 

 pellucid patch, the gas-gland (PI. VIII, fig. 5), which secretes air from the water into the air-sac. There 

 is one common digestive and circulatory space, stretching also round the air-sac, with which all the 

 daughter polyps and gonophores communicate, so that the products of digestion can reach all parts. 

 Waste products can diffuse out through the fine tissues, through which oxygen also can be taken up 

 from the sea; undigested refuse like fish-bones and scales can be got rid of again through the mouths 

 of the gastrozooids. 



The details of reproduction are still unknown, but probably terminal branches bearing the gono- 

 phores break off and are kept on the move by the asexual medusoids (swimming-bells). Fertilization 

 probably takes place in the sea. 



It was realized long ago that the long axis of Physalia takes up early in life a peculiar orientation in 

 the water. Whereas most siphonophores have the oral-aboral axis vertical, the overgrown air-sac of 

 Physalia topples over so to speak so that the long axis is horizontal. Circular and longitudinal sheets 

 of muscle are developed everywhere, so that the animal can turn and twist about, lengthen and shorten 

 its polyps and tentacles, and open wide and close its many mouths. 



Physalia appears to be very successful in avoiding being eaten except in the juvenile stage. It needs 

 no sense-organs to find food. Fishes as large as mackerel and flying fish bump into its tentacles and 

 provide much more food than Physalia can digest. When the surplus is jettisoned, many of the 

 attached feeding gastrozooids are lost, but this loss is quickly made good by the great proliferation of 

 buds, a faculty which may have arisen in consequence of the abundant food. 



Physalia is indeed an unusual sort of animal, an association of larval and adult individuals or 

 persons— as opposed to organs— which have been budded from the parent larva but which have not 

 become separated from it, the parent larva itself having developed a giant float to carry all these 

 individuals at the surface of the sea. 



APPEARANCE AND HABITS 



Physalia' s sky-blue, or light green, air-filled bladder with carmine-edged crest floats at the surface and 

 the animal drifts in the wind. The float may reach a length of 10 or 12 in. and its deep-blue trailing 

 tentacles, difficult to see when fully extended, can reach a length of 50 m. or more. The tentacles carry 

 enormous numbers of stinging-cells or nematocysts. 



The smallest specimens from Miami (PI. VII) measured 1-25 mm. in length. This is less than the 

 smallest, previously recorded by Huxley (1859), figured by him and probably taken in the spring of 

 1847 in the South Atlantic; it measured one-tenth of an inch (2-5 mm.) in length, though he gave it as 

 measuring one-fifth of an inch. The Miami collection of about 100 larval individuals (1-25-5 mm -) was 

 made on 20 January 1958 and reached me (in formalin) on 14 February. When the vial was opened 

 the animals were a beautiful turquoise-blue all over and were uniformly covered with nematocysts. 

 They were transferred to dishes of stock formalin neutralized with hexamine and covered with black 

 paper after being examined with a tungsten ribbon lamp. But next morning little colour remained. 



