DEPTHS IN THE NORTH ATLANTIC OCEAN. 209 



one of the former to several thousand of the hitter. And 

 owing to their rarity, and to the impossibility of separating 

 them from the other components of the Atlantic mud, it is very 

 difficult to subject them to a thorough examination. 



The coccospheres are of two types — the one comjjact, and 

 the other loose in texture. The largest of the former type 

 which I have met with measured about -i-rcnrth of an inch in 

 diameter (fig. 6 e) . They are hollow, irregularly flattened 

 spheroids, wdth a thick transparent wall, which sometimes 

 appears laminated. In this wall a number of oval bodies 

 (1), very much like the "•' corpuscles " of the cyatholiths, 

 are set, and each of these answers to one of the flattened facets 

 of the spheroidal wall. The corpuscles, which are about 

 _.^ij_^th of an inch long, are placed at tolerably equal distances, 

 and each is surrovmded by a contour line of corresponding form. 

 The contour lines surrounding adjacent corpuscles meet and 

 overlap more or less, sometimes appearing more or less poly- 

 gonal. Between the contour line and the margin of the 

 corpuscle the wall of the spheroid is clear and transparent. 

 There is no trace of anything answering to the granular zone 

 of the cyatholiths. 



Coccospheres of the compact type of y-=L_th to -n-J^y^th of 

 an inch in diameter occur under two forms, being sometimes 

 mere reductions of that just described, while, in other cases 

 (fig. 6, c), the corpuscles are round, and not more' than half to a 

 third as big (j , ooo ^h of an inch), though their number does 

 not seem to be greater. In still smaller coccospheres (fig. 6 a, b) 

 the corpuscles and the contour lines become less and less dis- 

 tinct and more minute until, in the smallest Avhich I have 

 observed, and which is only T-Wth of an inch in diameter 

 (fig. 6 a) they are hardly visible. 



The coccospheres of the loose type of structure run from 

 the same minuteness (fig. 7 a) up to nearly double the size of 

 the largest of the compact type, viz. ^-oth of an inch in 

 diameter. The largest, of which I have only seen one specimen 

 (fig. 7, d), is obviously made up of bodies resembling cyatho- 

 liths of the largest size in all particulars, except the absence 

 of the granular zone, of which there is no trace. I could not 

 clearly ascertain how they were held together, but a slight 

 pressure sufliced to separate them. 



The smaller ones (fig. 7 b, c, and a) are very similar to 

 those of the compact type represented in figs. 6, c and d ; 

 but they are obviously, in the case of b and c, made up of 

 bodies resembling cyatholiths (in all but the absence of the 

 granular zone), aggregated by their flat faces round a common 



