SYSTEMATIC AND BIOLOGICAL ACCOUNT 57 



round it, but leaves an oval area on the other side free. Under the spadix lies the nucleus. A similar 

 condition was figured by Weismann (1883, Taf. xxn, and p. 203) for Agalma rubrum {Stephanomia 

 rubra). Bracts are very characteristic in shape (Text-fig. 21). The bracteal canal terminates on a papilla 

 on the concave terminal facet. The presence of young bracteal buds of this characteristic form is the 

 criterion for identification of large pieces of the siphosome, and at once distinguish such pieces from 

 those of another antarctic physonect Stephanomia convolnta, whose young bracts have a terminal 

 sausage-shaped mass of nematocysts lying in the sagittal plane of the bracts, separating the two 

 oblique, dorso-lateral, terminal facets. The muscular lamellae of bracts and buds of bracts are closely 

 crowded together in at least six rows on either side of the gonophores in the contracted and preserved 

 material, and most of the gastrozooids are detached. 



Text-fig. 21. Marrus antarcticus gen.n., sp.n., WS St. 552E. A, B, two views of adult bract; 

 C, D, side of young bracts; E, gonophore, x 13. A, B, C, D x 12. 



Colour. There are colour notes on Antarctic physonects by members of ' Discovery ' staff made on 

 four occasions on board while sorting the plankton. They related to specimens of two physonect species 

 that turn out to be other than Pyrostephos vanhoeffeni. 



It has been a difficult matter to apply these notes because on each of the four occasions (Sts. 890, 

 2001, 2006 and 2010) all three Antarctic physonects were present in the catch; but, bearing in mind 

 that it is possible that I have made some mistake, the following collectors' notes appear to apply to 

 Marrus antarcticus: 



(1) Station 890, N 100 B. A large part of the siphosome (no nectosome) labelled 'Pyrostephos 

 vanhoeffeni ' ; ' typical deep brown colouring [probably applies to gastrozooids] central stalk portion 

 bright pink'. 



(2) Station 2001. 'Stolon deep orange crimson [this appears to refer to a specimen of the necto- 

 some, without nectophores, of Stephanomia convoluta]. Coloured part of bells [Marrus antarcticus] 

 very rich deep orange red.' 



