REPORT ON THE SIPHONOPHORjE. 237 



The family Forskalidse comprises those Physonectse polygastricse which have a long 

 tubular stem of the siphosome densely covered with bracts, and a strobiliform nectosome 

 composed of numerous spiral rows of nectophores. The siphons are very large, and 

 distinguished by a very long pedicle. They differ in these characters from most other 

 Physonectse, the nectosome of which is either biserial or quadriserial. The corona of 

 bracts of the Anthophysidse, however, may be compared with the spiral nectosome. 



Although the Forskalidse are the largest and the most splendid of all Physonectse, and 

 some species occur in the Mediterranean and the Atlantic in large numbers, nevertheless 

 they remained perfectly unknown up to the year 1841. In that year Milne-Edwards 

 published the first description of two Mediterranean species, under the names Stepha- 

 nomia contorta and Stephanomia prolifera (71, p. 217, pis. vii.-ix.). It was completed 

 twelve years afterwards by Kolliker, who established for them the genus Forskalia (4, 

 p. 2, Tafs. i., ii.). Additions were afterwards made by Leuckart (8), Vogt (5), Keferstein 

 and Ehlers (33), and Claus (35). Recently (1881) an Atlantic species of Forskalia has 

 been described by Fewkes, under the name Stephanomia atlantica (44, p. 264, pis. 

 v., vi.). Another Atlantic species, Forskalia tholoides, was observed by me in 1866 off 

 the Canary Islands, and is described in the following pages (Pis. VIII. -X.). 



A very remarkable and gigantic deep-sea Physonect, which probably belongs to this 

 family, was described in 1878 by Studer (40) under the name Bathypliysa abyssorum, 

 and in 1884 by Fewkes (45) as Pterophysa grandis. A similar form, of which I was able 

 to examine some fragments, makes it probable that these giants of the deep sea do not 

 belong to the Rhizophysidse (as the last-named author supposes) but to the Forskalidas. 

 Another new and interesting genus of this family, described in the following pages as 

 Strobalia, was observed by me in 1881 in the Indian Ocean, and illustrates the affinities 

 of this peculiar family. 



Nectosome. — The swimming apparatus in the Forskalidse is larger, stronger, and more 

 highly developed than in any other Physonectse. The pneumatophore at the apex of the 

 trunk is small, but the nectophores are very numerous (usually more than one hundred) 

 and arranged in a continuous spiral. The whole nectosome is sometimes cylindrical or 

 conical, at other times more campanulate or hemispherical ; its different forms are 

 comparable to those of the different cones of firs. Its rounded surface is elegantly 

 panelled or facetted by the basal ostia of the nectophores, which are regularly disposed 

 in a cjuincuncial manner. The spiral line which connects the basal insertions of the 

 nectophores has four to eight or more turnings, and is usually lasotropic, therefore 

 opposite to the dexiotropic spiral of the siphosome. The genus Forskaliopsis is dis- 

 tinguished by the possession of palpons which are scattered between the nectophores. 

 The physiological activity of the nectosome is more highly developed thau in all the other 

 Physonectse, since the great number of nectophores and their pointing in all directions 

 enables the animal to perform a greater variety of swimming motions. 



