ORDERS OF RII1ZOPODS— CHALLENGERIDA. 21 



instead of two, falls into four equal parts, and in others again (Protomonas, 

 Protomyxa, Myxastrum) at once into a large number of small globules of 

 slime, each of which again by simple growth becomes like the parent 

 body." * 



Sir Wyville Thomson, in the Voyage of the Challenger, briefly 

 describes certain Rhizopods, which he refers to a new order. On page 

 341 of the work indicated, he says: "In the investigations with the 

 towing-net, made by Mr. Murray during the latter part of the cruise, at all 

 depths, about thirty species or more were procured of a beautiful group of 

 minute forms approaching, but in many important points differing from the 

 Radiolarians. This order have apparently hitherto escaped observation, 

 and 1 retain for the type genus the name Challengeria, and for the Order that 

 of 'Challengerida'. As a ride these forms are extremely minute, although 

 some of them approach in size the smaller Radiolarians. They consist 

 usually of a single chamber of silica varying greatly in form, sometimes 

 triangular, sometimes lenticular, and frequently globular or flask-shaped ; 

 with a single opening usually guarded by a beautifully formed and fre- 

 quently highly-ornamented lip. The contents of the shell consist of a mass 

 of granular sarcode, with one or more large well defined granular nuclei, 

 and a number of dark brown, sometimes nearly black, rounded compound 

 granular masses. The Challengerida are essentially Rhizopods with mono- 

 thalamous siliceous shells ; and their zoological position may be not very far 

 from such forms as Gromia." 



Nothing is said of the characters of the pseudopods ; but should they 

 be of the same kind as those of Gromia, this, with the new forms, might 

 conveniently be associated in the same order. 



* NatUrliclie Schojifungsgeseliichte, 1872, 166. 



