352 ALFRED GIBBS BOURNE. 



any nephridia ; and their absence, if they are really absent, is 

 a very remarkable character, which I should be glad to see 

 verified. 



I found numerous individuals in which the generative organs 

 were well developed (PL XXVII, fig. 3). 



The testes occur in segments viii and ix, and the ovaries in 

 segment x. 



The spermathecae lie in segment v, and open near the modi- 

 fied genital setae, between segments v and vi. 



I was able to make a few observations on the asexual repro- 

 duction. 



The most complicated chain of zooids which I obtained ex- 

 hibited two regions of active growth. Such a chain would be 

 represented, according to the nomenclature which I adopt, 

 thus : — BC, or bo, or c^c^, &c. According to the same nomen- 

 clature, n=17 in P. littoralis, and z' consists of four 

 segments. 



Prist ina, Ehrenberg (see woodcut). 



Seven cephalized segments — of which only one,theperistomial 

 segment, is recognisable in the fully grown head region — may 

 be distinguished in the newly budded head region. 



The prostomial tentacle is short. 



The dorsal setee are capillary or capillary and spear-shaped. 



Branchial processes are absent. 



Eyes are absent in all the known species. 



1. P. longiset a, Ehrenberg. 



This species has been recently re-described by Vejdovsky. I 

 have not seen it, nor has it, so far as I know, ever been recorded 

 from England. 



2. P. equiseta, sp. n. 



I found this species in great quantity in the Victoria regia 

 tank in the gardens of the Royal Botanic Society at Regent's 

 Park, London. 



It differs from P.longiseta only in the non-development of 

 the long setae to which that species owes its name. 



