134 W. M. Bale . 



Plumularia uidivii<a, Bale, Jouin. Micr. Soc. Vict., ii., 



1881, p. 39, 46, pi. XV., %. 1. 

 Phimularia laxa. Allinan, Chall. Plum. 1883, p. 19, pi. i.,. 



figs. 5, 6. 

 Plumalarlu torresia. Von Lendenfeld. Proc. Lin. Soc. 



N.S.W., ix., 1884, p. 477, pi. xiii., figs. 13, 14, pi. liv., 



fig. 16. 

 Plumularia ruhru, Von Lendenfeld, Proc. Lin. Soc. N.S.W., 



ix., 1884, p. 476, pi. xiii., figs. 11, 12, pi. liv., fig. 15. 

 The simple form of this species was described by me in 1881 

 under the name of P. indivisa, but it was mentioned in an adden- 

 dum that it had been found to be identical with the stemless form 

 described by Busk. It is introduced hei'e for the purpose of recti- 

 fying its erroneous association by several Avriters with the widely- 

 distributed P. secundaria, consecjuent on Dr. Billard's report that 

 Busk's type specimen in the British Museum was the same as that 

 species. This statement is doubtless correct, being confirmed in 

 letters from both Dr. Billard and Di'. Kirkpatrick, nevertheless 

 Busk's account shows clearly that the specimens which he had before 

 him were not P. secu/idaiia : moreover, my specimens agree precisely 

 with those described by Busk. Obviously this is an instance, like 

 others I have met with, in whicli the museum specimen is erroneously 

 labelled; and in this case the confusion is not surprising, as the 

 two forms cannot be distinguished from each other without micro- 

 scopical examination, and, as I have now ascertained, both are 

 found in the same locality. 



Under the microscope the two hydroids are easily distinguished. 

 The short, stout, rigid or semi-rigid lateral sarcothecae of P. cam- 

 panula and its stemless variety, are in themselves sufficient to- 

 mark it as distinct from any species with the long, wine-glass-shaped 

 cups found in P. secundaria. P. catharina, etc.. as Busk points out. 

 Other differences are the presence in P. secundaria of a very small 

 sarcotheca behind the hydrotheca. not found in P. campanula, and 

 also the presence of one, two, or three, but generally two, median 

 sarcothecae on the uppei' part of each internode, where P. cam- 

 pa nuta has only one. 



The ramification of P. campanula is very variabU-. Kirst we 

 have the iridivisa-iovm, in which simple hydrocladia spring dirt'ctly 

 fioiii the hydroihiza. Among these we find shoots which give origin 

 to (inc. or perhaps two, secondary hydrocladia. From the^e the 

 tiansition is easy to regularly pinnate forms, such as constitute the 

 P. ruhra of Von Lendenfeld; and thence to the polysiphonic 



