l82 PORIFERA. II. 



secondary fibres. The network is partly polyspicular, partly unispicular, from one to four or five 

 spicules being found alongside. Some long fibres are found, especially distinct in the branches, in 

 which the}- run longitudinally; they are not thick, however, scarcely above o-03 mm . In the nodes of 

 the skeleton a little copious, white, and clear mass of spongin is found, but no spongin is seen in 

 the dermal skeleton. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli; they are either quite 

 straight or slightly curved. The point is rather short, at most middle long. The spinulation may be 

 somewhat varying, the spines being more or less powerful, but they are most frequently rather scat- 

 tered ; also in this feature, however, some variation is found. Next the spinulation is remarkable b\ 

 the fact that the spines are almost always a little closer gathered at the upper end, and that here 

 most frequently a few larger spines are found; especially in the thinner styli the spines are distinctly 

 more closely gathered at the upper end. The length varies from 0-208— o-274 mm . The thickness is very- 

 varying, from 0-0057 — o-oi28 mm ; this variation in thickness is in no proportion to the length; the thinner 

 ones being fully as long as the thick ones. Developmental forms of the styli, down to exceedingly 

 fine ones, are rather frequent; they are of about the full length; the finer ones are quite slightly 

 spined, they resemble most frequently subtylostvli, a little swelling being seen just below the upper 

 end, presumably corresponding to the closely gathered spines later found here. 2. The dermal 

 spicules are tylota or strongyla with spined ends and of a similar form as in the preceding species; 

 they are slightly and evenly curved; they may be about equally thick through their whole length, 

 but most frequently they are thickest in the middle; there may be a little difference between the two 

 ends, but most frequently they are almost quite equal. Their length is 0-19— o-25 mm , and the thickness 

 0-005— o-oo7 rom . Developmental forms were rather frequent, in which one end was always thinner than 

 the other, b. Microsclera are anisochelse palmatse of the ZopAon-type and bipocilla. 1. The aniso- 

 chelje are of the common form, the tooth is of about the same breadth as the alae and most frequently 

 a little shorter; the larger end has a long, narrow tuberculum, at the smaller end a shorter tuberculum 

 is found joining the spur. The chelae may be somewhat varying with regard to the length of the 

 free part of the shaft. Their total length varies from 0-017 — 0'03i m "', the breadth is proportionally 

 o - oo6 — o-oi28 mm . Some developmental forms at different stages were seen; the youngest ones are fine 

 staves recurved at the ends; the spur of the smaller end, which in reality is only a peculiar develop- 

 ment of the tuberculum, is already begun at an early stage. 2. The bipocilla are of the common 

 form, the indentation of the edge of the lower end is only seen with difficulty ; their length is 0-007 

 — o-oio mm . The microscleres are found throughout the tissue and especially in the dermal membrane. 



With regard to the spicules this species is chiefly distinguished from I. piceus by having upon 

 the whole smaller spicules, and by some difference in the spinulation of the acanthostyli; when this 

 fact is regarded in connection with the exteriors and modes of growth of the two species and with 

 the feature of their oscula and pores, the species are with certainty- to be distinguished from each 

 other. — As I have had a type specimen of Armauer Hansen's Reniera dubia for examination, I 

 have been able to identify the species with certainty. Armauer Hansen has not seen the micro- 

 scleres at all, and without an examination of the type specimen a determination would have been 

 quite impossible, as I think that Armauer Hansen's always bad drawings of spicula may be said 



