NOTES ON RETICULARIAN RHIZOPODA. 41 



retain their form are split and empty, as though the contents 

 had swollen to bursting before being dissolved out. Digestion 

 in these cases was not carried far enough to dissolve much of 

 the siliceous matter, and the split tubes therefore represented 

 the inorganic portion of the investment. 



There is no other Rhizopod to which Rhizammina can be 

 very accurately compared, but it has perhaps most in common 

 with the branching tubes of Hyperammina vagans : in point 

 of fact, it represents a very distinct type of organisation. 



The locality alluded to, in which it is so abundant, is the 

 " Challenger " Station, No. 299, lat. 33° 31' S. ; long. 74° 43' 

 W. ; that is, between the Island of Juan Fernandez and the 

 western coast of South America; depth 2160 fathoms. 



Genus — SAGENELLA, 7iov. 



{<Tay{]vr], a drag-net). 



SaGENELLA FRONDESCENS, 71. sp. PI. V, fig. 1.) 



Characters. — Test adherent ; consisting of long, finely 

 arenaceous covered passages, ramifying or forming a network 

 over the surface of shells or other bodies. Branches bifur- 

 cating, each limb terminating in a neatly rounded aperture. 

 Colour white to very light brown. Length indefinite ; 

 diameter of the larger passages g^ inch (0"4 millim.) of the 

 smaller branches ^7-^0 inch (0'12 millim.). 



This singular little organism occurs amongst the Nullipore 

 debris of shallow water in the South Pacific, in company with 

 other parasitic Rhizopoda, such as Placopsilina, Planorhulina, 

 and Truncatulina. There is possibly no other known in- 

 stance of a Foraminifer with a distinctly reticulating test, 

 either free or adherent, but it is not difficult to understand 

 how the inosculation of the passages takes place. The 

 branches commonly bifurcate at their extremities, and each 

 fresh branchlet, after growing about a thirtieth of an inch, 

 more or less, divides again in the same way; thus, however 

 irregular the growth, the sarcode projecting from the 

 different apertures must continually meet, and the ends 

 naturally coalesce ; the investment being formed as growth 

 proceeds, an irregular shelly network of necessity results. 

 The test is very finely arenaceous, and it appears to be really 

 tubular, that is to say, it is not a mere tent-like covering with- 

 out a floor proper to itself, like that of Webhina. It occurs in 

 little patches a quarter of an inch or more in diameter, of 

 white or light yellowish-brown colour. The ends of the 



