XXII. 



CHARACTERISTIC DEEP-SEA TYPES. -- RHIZOPODS. 



THERE must be, all over the bottom on which reticularian 

 rhizopods have been found, thousands of undiscovered minute 

 protozoans which have no solid tests. On account of the diffi- 

 culty of examining on the spot the samples of bottom as they 

 are brought up, we can only conjecture the physiology of these 

 lowest types, which will undoubtedly be discovered whenever the 

 proper methods for examination are employed. In the mean 

 time, we must be satisfied with a knowledge of the types which 

 have become known to us from their tests ; but even these 

 do not explain the structure of their animals ; this is known 

 to us only by comparison with that of their shallow-water 

 allies. 



No special report of the " Blake " Foraminifera has as yet 

 been completed, but I am fortunate in being able to extract from 

 the admirable memoirs of Brady on the " Challenger ' Fora- 

 minifera, and of Dr. Goes on the Rhizopoda of the Caribbean, 

 descriptions and figures of the principal types collected by us. 

 Dr. Goes, during a stay of several years at St. Bartholomew, 

 explored a considerable area with the dredge, to a depth of 

 400 fathoms, and, owing to the existence of extensive sunken 

 plateaux and steep sloping banks, where the temperature falls 

 rapidly, he was able to collect the majority of the types which 

 we subsequently brought together from deeper waters, but which 

 extend upwards to depths of 200 fathoms, or 150 even, and 

 perhaps less. 



Of the rhizopods the siliceous radiolarians play an unimpor- 

 tant part in the bottom deposits of the district explored by the 

 " Blake." A few surface species were collected in the track of 

 the Gulf Stream. Yet, judging from the well-known radiola- 



