26 



HYDROIDA 



below the polyp. The polyp wears a basal whorl of 20 — 35 tentacles up to 40 mm. long; the distal 

 tentacles, up to 3 mm. long, are densely crowded round the orifice in a whorl consisting of several rows. 

 The female gonophores are eumedusoid with 3 — 6 external longitudinal ribs and as many 

 corresponding radial canals. The male gonophores are cryptomedusoid and oval, often with an attempt 

 to be pointed in the distal part. The gonophores are born upon up to 20 blastostyles, which attain a 

 length of 35 mm. The actinula larvae, when deliberated, wear filiform tentacles. 



Material : 



Between the Faroe Islands and the Shetlauds, depth 505 fathoms. 



Tubularia regalis presents so many points of resemblance to Titbularia indivisa that the risk of 

 confounding the two species is very easily incurred. As a general rule, the full-grown polyps of Tu- 



20om. 600m. ._ 100a m. 3000m. 



Text-fig. E. The occurence of Tubularia regalis in the Northern Atlantic. 



bularia regalis are larger than those of Tubularia indivisa. But this is not the case in younger 

 individuals of Tubularia regalis, in which consequently the only certain distinguishing marks are pre- 

 sented by the gonophores. The gonophores, indeed, are typical enough in the female individuals, but 

 are not very conspicuous in the male ones, especially at earlier stages. The male gonophores of Tu- 

 bularia regalis are oval, while those of Tubularia indivisa are globular. It is evident from the diag- 

 nosis of the species, that also Tubularia regalis presents a strong sexual dimorphism. The first who 

 got aware of this fact, was Swenauder (1903), who accordingly pointed out that the female had been 

 described as a different species Tubularia. variabilis Bonne vie. 



Tubularia regalis is a form of true Arctic character, particularly occurring in the deeper 

 parts of the cold area. In the seas far towards the north it rises to shallower parts, and it is, for instance, 



