22 DISCOVERY REPORTS 



with the pellets of any animals which quite correspond with this type, those of the 

 mollusc Aplysia punctata have a similar outer layer, enclosing an inner pellet of different 

 shape, while those of many molluscs have spiral groovings on the surface, and in extreme 

 forms the pellet may be in the form of a spirally twisted rod. It is easy to imagine the 

 conjunction of these two types giving rise to an ovoid pellet with a spiral core, as 

 described above. 



Galliher (1931) has described, under the name of "Sporbo", structures which are 

 apparently fossilized pellets of this same ovoid shape, from Miocene oil shales in 

 America, and in a later paper (1932) he compares these with similar recent pellets from 

 the Clyde. With the exception of hardening, and in many cases pyritization of the 

 former, they appear to be very similar. 



Thorp (1931) describes three stations off the coast of Panama, on the Atlantic side, 

 in depths of 3595, 2131 and 3445 m. respectively, in which pellets form 26-1, 38-1 and 

 44-1 per cent of the mud ; and of thirty- two stations described by him from the western 

 North Atlantic and Caribbean Sea, sixteen are recorded as containing such pellets. With 

 regard to the origin of these, however, he is very doubtful. He says : " The size and shape 

 of the individual ovoid suggest an organic excrement but the preservation for any 

 length of time of such an object appears doubtful. Bacteria would find nourishment in 

 the unassimilated food of higher organisms. As a result most of the remains would be 

 converted into gaseous and water-soluble products. These in turn would be dispersed 

 by the sea water. It appears more probable that chemical and physical aggregation is 

 responsible for the formation of these objects". 



In the case of the pellets found in the Clyde it has been definitely shown that they are 

 animal products (Moore, 193 1), and furthermore that they are able to retain their form 

 as well as their differentiation from the surrounding mud for periods of at least a 

 hundred years. At the end of this period they are quite as definite as they were when 

 they were first formed, and there is no reason to suppose that any new agencies come 

 into play to cause their breakdown after that time. At any rate bacteria are known to be 

 abundant throughout the whole of the time, and at all depths in the mud (Lloyd, 193 1). 

 In the Discovery material there was a type of pellet which was very abundant in 

 some of the plankton nettings. Samples were examined from Stations 549, and WS 399, 

 and the pellets in them were almost certainly those of Euphausia siiperba, which is very 

 abundant in the plankton there. They agree in form with those in the gut of the animal, 

 as well as with those described from other euphausids from the Clyde (Moore, 193 1 a). 

 No pellets of this type were observed in any of the bottom deposits, which was probably 

 due to their quick breakdown as was the case in the Clyde, where pellets of euphausids 

 and of Calamis finmarchiciis could be seen abundantly on the extreme surface of the 

 mud, but were never recognizable below the surface. 



The pellets from the bottom deposits fall into two classes, rod-shaped and ovoid, of 

 which the latter were numerically by far the most abundant. They occur at various 

 stations and at all depths, and though their size and shape vary slightly, they are all of 

 the same general type. The details of these are given in the table on page 24. Since 



