On the Development of Aurelia aurita. 333 



polype, commonly known as Hydra tuba. The ova producing them 

 are doubtless introduced with the sea-water ; and if the conditions 

 are suitable for their development, the rock-work and sides of the 

 tank are often studded with hundreds of their delicate transparent 

 bells. The changes they undergo before assuming the adult form 

 have been investigated by Sars, Siebold, and many other naturalists ; 

 and it is now well known that these little polypoid forms are only 

 early states of Aurelia ai/rita — the medusa seen thronging our coasts 

 in such countless thousands during the summer months. The per- 

 fect animal, however, is so rarely produced within the limits of an 

 aquarium, that a recent case of its occurrence in one of the Society's 

 tanks appears to me worthy of record. Since the establishment of 

 the Fish house in the Zoological Gardens, not a year has passed 

 without the abundant production of the polypes in several of the 

 tanks, and their transverse splitting and change to medusoids have 

 been frequently observed ; but no further development has taken 

 place, and after a short period the young animals have gradually 

 disappeared. In the present year, however, greater success has been 

 attained ; and this is perhaps partly due to the water in the tank 

 having been kept at a nearly uniform temperature, from the absence 

 of any severe cold during the early part of the season. The polypes 

 made their usual appearance about the end of January ; and after 

 two or three weeks a considerable number of medusoids were de- 

 tached, of which a few only have survived ; but some of these now 

 exhibit all the specific characters of the perfect Medusa, the largest 

 specimen at the present time being 3 inches in breadth when dilated, 

 and the others of various intermediate sizes. It is unnecessary to 

 detail here the gx'adual changes undergone in the course of deve- 

 lopment to the perfect animal, as they have been fully and accurately 

 described by several authors : I will only mention that an instance 

 was observed of two medusoids having been thrown off together from 

 the parent stock, and remaining united for more than a week : each 

 gave evidence of independent existence ; and their course through 

 the water was marked by great irregularity, from the uncertain and 

 sometimes opposite action of the two disks. 



The water containing these Medusae has remained for several 

 months unchanged ; but its purity has not been endangered by the 

 presence of fish, or other animals requiring a large supply of oxygen. 



Indications of the Existence of a Second Species of 

 Emeu (Drom.eus). By A. D. Bartlett. 



The specimen of Dromceus now exhibited was obtained with others 

 far in the interior of South Australia, several hundred miles from 

 Port Philip. 



It differs from Dromceus XovcB-holtandice in having the whole of 

 the feathers of the body distinctly marked with narrow transverse bars 

 of light grey and dark brownish black. The feathers of the back 

 and sides of the bird are broader and longer and less silky in texture 

 than those of the common species : that this is so, is quite evident 

 to the touch. The upper part of the neck and head is nearly black ; 



