PORIFERA. II. 37 



fig. i d, PI. X. The smaller the chela, the smaller is the free middle part of the shaft in proportion to 

 the ends, which are, accordingly, comparatively longer than in the larger chelae. The length of the 

 chelse varies between 0020 — o-045 mm , the breadth between 0-007 — o-oi5 mm , and the thickness of the shaft 

 between o - ooi — o - oo2 mm . In several of the individuals developmental forms are found abundantly, corre- 

 sponding to all sizes of the chelae; the youngest forms are so fine as to be observed only with diffi- 

 culty, of a thickness of ca. o - ooo5' nm . These fine forms consist only of the axis, which is already of full 

 length. From these voungest forms and to the fully developed chela all transitional forms are found. 

 Of the cheke the small ones are present in by far the largest number, while the large ones are more 

 scarce, and do not appear to be found in all individuals, some being found, in which the greatest 

 observed length of the chela is ca. 0'028 mm . The chelse are found throughout the sponge; the largest 

 may occur in rosettes, but this fact has only been observed in very few cases; also Merejkowsky 

 mentions rosettes. 



Remarks: When Schmidt, in 1870, established this species he referred it to the genus Cl/a- 

 linula, overlooking the chelae, and in 1875 he made the same mistake. Also Grentzenberg 1. c. 

 must have failed to see the chelse, there being no reason to doubt that it has really been the present 

 species he has had before him. hevinsen was the first who, in 1893, when examining the type 

 specimen of Schmidt, which is found in our museum, discovered the chelse, and referred the species 

 to the proper genus. In 1875 Schmidt 1. c. established a species Mycalc (Esperia) lanugo; the de- 

 scription, as is generally the case, is exceedingly brief, and no figures are given. It is, however, said 

 of the chelse that they are distinguished by the smaller end being larger than is else the case in 

 Espcrclla, and that in a few chelse both ends are equal, and just this fact is a very characteristic 

 mark of M. ovulum. The terms used of the exterior, correspond also very well, it being said that 

 it is roundish «von weicher, flockiger Beschaffeuheit» , which latter character Schmidt has even 

 expressed in the name. Now it is a fact that specimens of ovulum sometimes, especially when of a 

 whitish colour, may have a peculiar, woolly appearance, about like a little lump of wadding. In 1891 

 Grentzenberg 1. c. enumerates E. lanugo, and gives figures of it, and to judge both from the habitus 

 figure and the rather bad figure of the chela, as well as from the whole description, there can be no 

 doubt that the species is identical with ovulum 1 ). This, again, corroborates the referring of Schmidt's 

 lanugo to ovulum; for, as far as can be seen, Grentzenberg has of this species only had the 

 material of Schmidt. Thus we find the peculiarity that as well Schmidt as Grentzenberg has, 

 both of them and each in a work of his own, enumerated one species as two different ones, partly as 

 Chalinula ovulum, partly as Esperclla lanugo; this peculiarity, however, may so far be understood, as 

 the reason is that in one case the chelse have been overlooked. 



Under E. lanugo Grentzenberg mentions that besides the common skeleton it possesses ein 

 aus Fasern gebildetes Geriist, dass Schmidt nicht erwahnt . He describes further that in a transverse 

 section is seen about in the middle of the sponge a circular fibre, inside of which run four or five 

 radiate ones coalescing in the middle. He figures this structure in fig. 24. The author thinks these 

 fibres to be spongin fibres, and he mentions some cells which are said to form those fibres in a 



'; I have later had the opportunity of examining a type specimen of M. lanugo, which proved the species to be 

 identical with ovulum. 



