452 DR. S. F. IIARMER ON THE 



The sessile statoblasts are very variable in shape and size 

 (figs. 23-25), but they are all larger than the floating statoblasts 

 of the same specimens. The largest one found measured 640 /.t 

 by 432 p, giving a ratio of 1-481 : 1. A shorter and broader 

 one was 560 /x by 480 fx, with a ratio of l'I66 : 1. The average 

 of seven measurements was 554 ^ by 434 /u, with a ratio of 

 1-276: 1. 



(4) Plumatella emarginata Allman, var. muscosa Kraepelin. 

 (PL LXIIL figs. 15-20.) 



In his well-known work on the German Freshwater Polyzoa, 

 Kraepelin (87) refers the forms of Plumatella which have come 

 under his observation to three species. These are described 

 respectively as P. princeps, P. polymorpha, and P. punctfitcc. 

 For the last, with which it is not necessary for me to deal, he 

 has adopted Hancock's name. The first two were renamed by 

 him, on the ground (pp. 118, 119) that the older names, from 

 which a choice might have been made, have been used in so 

 many difierent senses by previous authors that it would only 

 have introduced additional confusion to have made use of any of 

 them for the species as characterised by him. I do not think it 

 necessary to follow Kraepelin m this conclusion. 



P. princeps and P. poh/morpha were distinguished principally 

 by the form of the floating statoblasts. In P. pi^lnceps these n.re 

 relatively long and narrow, and the ratio of length to breadth is 

 said to vary from 1"53 : 1 to 2-79 : 1, the typical ratio being given 

 as about 1-8 : 1. The species thus characterised includes P. einar- 

 ginata Allman and P.fntticosa Allman. 



In P. polymorpha the floating statoblasts are broader in pro- 

 portion to their length, and the ratio of length to breadth is 

 described as varying from 1-1:1 to 1-42 : 1 ; the average being 

 about 1-25:1. tinder this name Kraepelin includes P. repens 

 and P. fungosa auctt. 



The forms of Plumatella with relatively broad statoblasts are 

 represented in the material which I have received from English 

 waterworks only by a variety of P. fungosa, which, following 

 Braem's earlier opinion, I have treated above as a species distinct 

 f fom P. repens. Those with elongated statoblasts ai-e i^epresented 

 by the material from Torquay, and it thus becomes necessary 

 to discuss the question of the name which should be used in 

 describing them. 



Braem (90, pp. 9, 10) has brought forward arguments to show 

 that P. frtiticosa and P. emarginata ai-e distinct species ; and he 

 points out the following differences between them : — 



(1) P . fruticosa has relatively slender tubes, which grow into an 

 erect form ; while P. emarginata has broader tubes, which ai'e 

 more adherent to the substratum. (2) The floating statoblasts of 

 P. fruticosa are more than twice as long as broad (average ratio ; 



