50 THAUMANTIAS HEMISPH^RICA: 



It is very probable that, under the name of " Medusa hemisphcerica" the older and most 

 of the more recent writers on Acalepha confounded many, or at least more than one, species 

 of Thaumantias ; and, as very few of their notices extend to more than characters obvious at 

 first glance, and common to a majority of members of the genus, it is difficult or impossible to 

 ascertain what form or forms were meant when the name in question was cited. The figures 

 given by Miiller and Gronovius were evidently at such times borne in mind; but, as 

 the importance of ascertaining the number and structure of the bulbous bases of the 

 tentacula was not understood by any of the naturahsts from whom I have igiven citations, 

 unless Peron and Lesson be excepted, the reference to those figures cannot be received 

 without suspicion. 



I feel sure that the animal I am about to describe and figure as Thaumantias 

 hemisphcBrica, is identical with that which was delineated by Miiller in the Zoologia Danica, 

 and clearly characterised by Peron, whose description, which I here cite, applies to no other, and 

 was probably drawn up after a study of Miiller's account and figure, for the French naturalist 

 gives no other locality than " des cotes de Danemarck." He characterises the species thus : 

 " un ombrelle hemispherique, deprime a son centre ; ovaires pedicelles et claviformes ; rebord 

 entier, garni de trente-deux tentacules tres-courts et de trente-deux petites glandes ; ombrelle 

 gris-bleuatre, parseme de petits points plus gris ; ovaires jaunatres, glandes marginales rouge ; 

 1 centimetre." The short diagnosis of Eschscholtz, "canalibus versus marginem disci 

 clavatis," founded on his misapprehension of the nature of the reproductive organs, would 

 apply equally well to half the allied species here described, and his account of the number of 

 marginal tentacles, "ihr Rand ist mit 16 bis 24 kurzen Fangfaden besetzt," leaves us in no 

 more certain position. The tentacles, however, as I have found by examination of very 

 numerous specimens, do vary greatly in the several stages of the animal's growth, though I 

 have never seen them fewer than twenty. When full grown, the number is, as Peron has 

 stated, thirty-six. This variation of number of tentacles with age is seen in several species of 

 Thaumantias, especially in those with depressed umbrellas. Many species, however, present 

 exactly the same number in their earliest and their oldest stages. Fortunately, the large 

 conspicuous red or orange oceUi, and brightly coloured claviform reproductive glands, afford 

 features combined with form, which will always enable us to recognise the true Thaumantias 

 hemispheerica without much difficulty. 



The individuals which I have examined in Zetland, where they abound in the bays and 

 harbours, have a hemispheric, sHghtly depressed, transparent, smooth umbrella, sometimes 

 measuring nearly three fourths of an inch across. The margin in adult specimens usually 

 bears thirty-two (sometimes more) tentacles, springing from as many large tubercle-like ocelli 

 which are vividly coloured with orange and red, and when magnified, are seen to present a 

 small black dot. The formula for the oceUi and tentacles in the adult is probably 7x4-f 4. 

 The tentacles are composed of granular tissue ; they are often carried short, not by contrac- 

 tion, but by coiling up in a spiral. The sub-umbrella is moderately convex, and divided 

 by the four gastric vessels, which pass in the lower half of their courses through four 

 hnear, claviform, purplish or yellowish ovaries, marked with purple or orange lines. The 

 stomach is short, rather broad, purpUsh, or tinged with pink, terminating in four lanceolate 

 fimbriated lips. 



The abundance of individuals of this species in all stages of growth enabled me, when 



