462 UE. fi. 1. BEOwiTB oU [Mat. 1?, 



Fam. BouqainviIiLIDjE. 



Perigonimtjs bbfbns (Wriglit). 

 Hydroid Form, 



Atradylis repens, Wright* (1858) ; Alder* (1862). 



Pcriyonimus rejpens, Hiucks* (1868) ; Allmau* (1872) ; Winther 

 (1880); Duerdin(1893); Garstang* (1894). 



Perigonimus mimitiis, AUman* (1863) ; Hincks* (1868) ; Allman* 

 (1872). 



Medusoid Form. 



Periyonimus repens, Crawford (1895). 



At Plymouth, on September 2nd, 1893, I placed a colony of 

 Periyonimus repens in a jar of sea-water. On the following day 

 about a dozen medusae were budded off. On the 13th another two 

 dozen were swimming in the jar from the same colony. None of 

 the medusae showed any signs of further development after their 

 liberation from the hydroid colony. 



The umbrella of the medusa is about f mm. in length and width. 

 There are two opposite perradial tentacles and two opposite per- 

 radial bulbs, without tentacles. Some of the specimens have a 

 knob at the aboral end of the umbrella. The knob varies in size 

 and shape in different individuals, in a few it is absent. 



Mr. W. Garstang sent me a colony from Plymouth, on March 

 17th, 1894. On the 19th two medusis were budded off, one with 

 a short knob at the aboral end of the umbrella, the other without 

 a knob. Unfortunately 1 was not able to keep these medusa 

 alive long enough toobaerve any further changes. Wright (1861) 

 states that he has kept the medusa until it had four perradial 

 tentacles and four interradial bulbs. 



Allman (1863) described another hydroid, Periyonimus minutus, 

 which, he states, is very much like Periyonhmcs repens. The chief 

 difference is in the shape of the medusoid, which has a constriction 

 across the aboral end of the umbrella. The figure given by 

 Allman of this medusa agrees with the specimens with a conical 

 knob, bred in my jars. Hincks (1868) has placed Periyonimus 

 minutus as a synonym of Periyonimus repeiis ; but Allman (1872) 

 has again separated them into two distinct species. As I have 

 obtained from the same colony medusce similar to Wright's figures 

 of Periyonimus repens and to Allman's figures of Periyonimus 

 minutus, I do not now see any reason for their separation into two 

 distinct species. 



DisTEiBunoN. Denmark, Baltic Sea, Winther (H). Heligoland, 

 Hartlauh (H). 



Scotland — Shetland Islands, Allman (H). St. Andrews, Craw- 

 ford (M). Firth of Forth, WriyU (H). 



England — Cullercoats (Northumberland), Alder (H). Plymouth, 

 Garstang and E. T. B. (H). Ilfraeombe, Hincks (H). 



Ireland— S.W. Coast, Duerdin (H). 



