Ch. XXI.] VABIOUS FOEMS OF ACALEPHS. 363 



The only exception I met with to the rule I have men- 

 tioned (namely, that when Hydrozoa floated, they appeared 

 in considerable shoals of one species only) occurred in the 

 great calms which we encountered in the North Atlantic 

 Ocean, in the first fortnight of July, and which extended 

 more or less over upwards of a thousand miles, during 

 which, on two or three occasions, I saw several species of 

 Hydrozoa mingled with vast numbers of compound Asci- 

 dians. Some of them were new and strange forms of Be- 

 rooids, with lateral expansive lobes upon which iridescent 

 bands of ciHa were placed, and approaching in appearance 

 the genus Eucharis of Escholtz. One of these is figured 

 at the head of Chapter XXIV. Some were abundant, 

 others but few in number, only appearing occasionally, and 

 therefore very difficult to capture from a moving ship. One 

 of these I did succeed in taking; but there were at least 

 three or four species besides the Velellse and Physaliae. 



The most magnificent specimens of the last-named richly 

 coloured animals (Physalise) occurred in the Atlantic Ocean, 

 near the Equator. On the 19th of June, in lat. 13° S. and 

 long. 22° W., wind S.S.E., therm. 77°, bar. 30°-10, the sea 

 was moderately cahn, and from time to time during the day 

 splendid individuals of Physalia pelagica sailed by, attracting 

 attention, even when far off, by their large size and brilliant 

 colours. They had the appearanc* of beautiful prismatic 

 shells standing upright upon rich blue cushions, the shell 

 being radiated fi-om the base or cushion to the circum- 

 ference, which was fringed with a rich and bright rose- 

 colour. They were not in great ahundance, but one would 

 float by every five minutes or so. 



The largest Physalia which I ex:amined measured as 

 follows : — 



