492 Ma. E. T. BBOWNE osT [Mar. 17, 



reproductive organs form a small oval swelling about halfway 

 down each of the four radial canals. In some of the specimens 

 belonging to this stage the stomach is prolonged into the substance 

 of the umbrella. The prolongation or apical stalk disappears in 

 the later stages, but its presence indicates in some species that the 

 medusa has not long been liberated from its hydroid. The mouth 

 Las four small lips. 



2nd Stage. Eight tentacles. — The interradial tentacle -bulbs 

 belonging to the first stage develop tentacles, and a few adradial 

 tentacle-bulbs begin to appear. The marginal vesicles never exceed 

 eight even in the adult form, but the otoliths show an increase in 

 number. At this stage sometimes four otoliths may be present, 

 but usually two or three. Width of the umbrella about 3 mm. 

 and slightly less in height. 



^rd Stage. Sivteen tentacles. — The adradial tentacles appear in 

 no definite order, and when they reach nearly their full size other 

 tentacle-bulbs commence to grow. The generative organs form a 

 long oval patch upon the radial canals. The otoliths in each 

 vesicle vary from two to four. Diameter of the umbrella 4 to 

 5 mm. 



Adult Form. (Plate XVII. fig. 2.) — I place under this head all 

 specimens with more than 16 tentacles. They increase in number 

 until 32 is reached, but this number may not be the maxiuiinn, 

 though it is tho most I have seen in a specimen. The marginal 

 vesicles always remain eight in nurrber, one of the characteristic 

 features of the species and by which it may be distinguished from 

 •Phialidium temporarmm. The otoliths in the vesicles show con- 

 siderable variation even in the same individual. Three or four 

 appear to be about the usual number present but sometimes more. 

 One specimen had five to eight otoliths. The umbrella becomes 

 very thick especially at the aboral end. By the thickness of the 

 umbrella I could usually recognize this species in an aquarium 

 when in company with Phialidium temporarium. 



The generative cells, which in the earliest stage form a small 

 oval patch about halfway down each radial canal, gradually grow 

 downwards or outwards but do not touch the margin. Usually 

 of a yellowish-brown colour. 



The largest specimen seen measured 13 mm. in width and 4 mm. 

 in height. During my visit to Plymouth in September 1893 I 

 saw several specimens of this medusa, belonging to the 1st and 2nd 

 stages, and some early stages at Port Erin in May 1894. 



According to Haeckel this medusa, possessing only eight mar- 

 ginal vesic'es and no cirri, ought to be placed in the genus Tiaropsis. 

 But as the medusa is more like the species hAnngmgio Phialidium 

 than Tiaropsis, I prefer to place it temporarily in the genus Phia- 

 lidium, until its hydroid has been found, rather than make a new 

 genus. 



Edtima iKSiGHis (Keferstein). 

 Sifhonorhynehus insignis, Keferstein (1862). 



