38 TIMA BAIRDII. 



* 



his time and sacrificing his professional pursuits to his favorite science, is now one of the 

 unselfish band of worthy assistants in the National Museum. 



Dr. Johnston met with the Tima Bairdii in Berwick Bay, on the 27th of September, 

 1832, floating on the surface of the water; and published an account of it in Loudon's 

 Magazine for the following year, illustrating his description by an expressive sketch from the 

 pencil of his accomplished and esteemed lady, to whom, as to her eminent husband, our 

 science owes many debts of gratitude. He describes it as " a semi-globular mass of a perfectly 

 translucent and almost colourless jelly, divided by four opaque, milk-white, narrow ligaments, 

 or bands, into four equal compartments. These bands arise at the angles of the mouth, and 

 are at first very fine, but become broader and somewhat curled in their course towards the 

 upper surface. The very dehcate membrane investing the body is folded at the margin, 

 which is furnished with a circle of rather distant, tapered, white tentacula. In our specimen there 

 were thirteen of these. The under side is produced in the middle, so as to form a kind of stalk, 

 at the apex of which is the mouth, of a square form, and encircled by four plumose branchial 

 appendages. When magnified, these are shown to be formed of a thin membrane, beautifully 

 but irregularly folded, like a frill, and edged with a neat thickened border. Diancea Bairdii 

 seems to be invested with two membranes, of great tenuity. The outer one covers all, like as 

 it were a glass inverted over a smaller globe, the intermediate space being occupied with a 

 consistent but colourless jelly, in which neither vessels nor membranes can be distinguished. 

 This coat forms two loose folds around the circumference, from the innermost of which tiie 

 tentacula arise, and the inner coat is probably a continuation of the outer reflected upwards ; 

 but it is not a simple membrane, since several laminae can be perceived to cross the body. 

 The white conical bands adhere to this inner envelope ; they are not muscular, but very 

 probably belong to the generative system. I consider the plumose processes at the oral 

 aperture as subservient to respiration, partly because of their position, and partly becau.?e of 

 their folded structure ; intended, as it appears to be, to expose the largest possible surface to 

 the action of the water. This Medusa is a luminous species. It gives out a copious light of a 

 whitish colour, when the water in which it swims is agitated, or when it comes in contact with 

 foreign bodies." 



Dr. Johnston compares it with a minute phosphorescent Medusa taken by Dr. Baird in 

 the Straits of Malacca, and considers the two identical. In all probability, however, they are 

 quite distinct, though congeneric. 



During the winter of 1839, I met with this handsome Medusa in two localities : first, in 

 the harbour at Burtisland, in the Frith of Forth, and afterwards at St. Andrews, where a 

 number of individuals were cast ashore on the sands, along with Cydippe pileus, and 

 C. Flemingii, and Aurelia aurita, after a very stormy night. 



The umbrella, in the specimens I examined and drew, was hemispheric, or rather cam- 

 panulate, with a slight constriction, giving it an elegant undulation about the upper third. 

 It varies, however, much in form. It is smooth, transparent, and colourless. The margin 

 bears sixteen tentacula, usually contracted, and tinged with pale pink. Between the tentacles 

 there is the appearance as of a scalloped veil. The sub-umbrella is truncated, and marked by 

 four radiating vessels, opening into a circular marginal one. In the course of these four 

 vessels appear to be four very narrow, linear, whitish reproductive glands. From the centre 

 of the sub-umbrella depends an ample cylindrical peduncle, extending for about a third of its 



