

308 COELENTERATA HYDROZOA chap. 



Apolemia this genus attains a length of two or three metres. 

 Mediterranean Sea. Dicymba, Indian Ocean. 



Physophorinae. The pneumatophore larger in proportion 

 than it is in the preceding families. The stolon is short, and 

 bears rows of nectocalyces at the upper end. The gastro- 

 zooids, dactylozooids, and gonozooids are arranged in verticils 

 on the lower expanded part of the stolon. Hydrophyllia 

 absent. Physophora, cosmopolitan in the areas of warm sea 

 water. 



Fam. 2. Auronectidae. The pneumatophore is large. The 

 stolon is reduced to a spongy mass of tissue on the under side of 

 the pneumatophore, and this bears numerous cormidia arranged 

 in a helicoid spiral. Projecting from the base of the pneumato- 

 phore there is a peculiar organ called the " aurophore," provided 

 with an apical pore. This organ has been described as a specially 

 modified nectocalyx, but it is probably a specialised develop- 

 ment of the epithelium-lined portion of the pneumatophore of 

 other Physophorae. The Auronectidae are found only at con- 

 siderable depths, 300 to 1400 fathoms, and are probably specially 

 adapted to that habitat, Bhodalia, Stephalia, Atlantic Ocean. 



Fam. 3. Rhizophysaliidae. The pneumatophore is large, or 

 very large, in this family, The zooids are arranged in horizontal 

 rows on the under side of the pneumatophore {Physalia), or in a 

 helicoid spiral on a short stolon (Epibulia). There are no necto- 

 calyces nor hydrophyllia. 



The genus Physalia is the notorious " Portuguese Man-of-War." 

 The pneumatophore is a large bladder -like vesicle, sometimes 

 attaining a length of 1 2 cm. One species described by Haeckel 

 under the generic name Caravella has a pneumatophore 30 cm. 

 and more in length, and dactylozooids attaining a length of 20 

 metres. It is a curious fact that only the male colonies of 

 Physalia are known, and it is suggested that the female may 

 have quite a different form. 1 Epibulia has a much smaller bladder 

 than Physalia. Both genera have a cosmopolitan distribution 

 at the surface of the warm seas. 



Fam. 4. Chondrophoridae. This family stands quite by 

 itself in the sub-order Physophorae, and is placed in a separate 

 division of the sub-order by Chun, who gives it the name Tracheo- 

 physa. The essential distinguishing characters of the family are 



1 Brooks and Conklin, Johns Hopkins Univ. Circ. x. 1891, No. 88. 



I 



