28 



moreover we find the parenchyma compacter in the latter specimens (trop. tuberosa) than in 

 the former (trop. pyramidalis). But we know by Thiele (1898 p. 43) that in S. panis (which 

 we identified with 92a-!; cf. p. 25) is "merkwürdig. . . das verschiedene Verhalten der Kloaken, 

 die bei manchen Exemplaren recht bedeutende Grosse erreichen, bei anderen kleiner sind uncl 

 bei noch anderen ganz zu fehlen scheinen". We see, consequently, that neither the external 

 appearance, nor the structure, nor the spiculation furnishes specific characters; the extremes 

 differ considerably, but they are united by all possible transitions. 



There is a great external resemblance between on one hand 426 a and 426 c which we 

 saw belonged to trop. pyramidalis, and on the other hand 948 a and 948 f, belonging to trop. 

 digitata. They differ on account of the total absence of robust spinispirae in the latter. We 

 found, however, in the above mentioned cases of wilsoni and cunctatrix that these spicules are 

 very variable and even disappear. Moreover we see that there is a considerable difference with 

 regard to their frequency. Robust spinispirae are abundant in 426 d ; compared herewith they 

 are not very frequent in 426a and 426b; still less frequent they are in 426c Also they are 

 less developed in the latter. The presence or absence of these spicules is, therefore, not of 

 specific value. It is beyoncl doubt that 948 a-f are all identical. Longitudinal sections across the 

 entire sponge show, however, many differences. In 948 a and 948 e we find a rather massive 

 tissue with comparatively narrow central canals, the whole making the impression of contraction. 

 Similar sections through 948 b or 948 g show a looser parenchyma and wider canals, entirely 

 resembling sections of 426 a-c, as can be seen on PI. V, figs. 1 and 3. In addition to the 

 large central canal, secondary canals are visible, more or less parallel to the former. We can 

 follow step for step how nearly 426 a-c and 948 a-f are allied ; and the same we see between 

 some specimens of 948 a-f and 426 c!. Consequently we find it impossible to separate 948 a-f 

 specifically from 426 a-c or 426 c!. As to the shape of the processes we see the same gradual 

 transitions. In the main, pyramidal process of 426a the ratio between the height and the diameter 

 at the base is about 6:8; in 948c! it is 6:3; but in 948e it is 6:5, in 948 f 6 : 6 etc. The 

 processes are generally conical, but not always-, they may be cylindrical or even somewhat 

 broadened at the top, thus resembling 5". tentorioides. Dendv hesitated to consider this "species" 

 as another "variety" of vagabunda, because of the presence of stout spinispirae in the former. 

 I believe the distinguished spongiologist would have had less scrupules if he had been acquainted 

 with the above facts. Indeed S. tentorioides by its structure, especially by the arrangement of 

 the main canals comes nearer 5". vagabunda. But by its spinispirae it forms a link between 

 948 a-f and 426 a-c , a form which might be placed among trop. digitata as well as among 

 trop. pyramidalis. Taking all together we arrive at the conclusion that digitata, tuberosa and 

 pyramidalis are three tropi but one single species. 



Spirastrella solida (B.M. 26) externally closely resembles 426c!; it differs in this respect 

 from 5. papillosa only by less prominent tubercles. Ridley & Dendy say that the robust 

 spinispirae, which are found in papillosa (and also in 426 c!) do not occur in S. solida. However, 

 I found such spicules here and there in the very type, B. M. 26- We saw already that this 

 sort of spinispirae, abundant in 426(1, are less frequent in 426 a and 426 b, still less in 426 c; 

 we have in B. M. 26 an example in which they are really very rare. 



