12 



PORII-KRA. II. 



or about straight. The alse do not continue so far down the shaft, so that the free middle part of 

 the shaft is about one third of the whole length or thereabout. The lateral edges of as well the 

 alse as the tooth diverge towards the middle of the chela, the terminal parts of which thus get a 

 triangular form. The lateral edges of both the alse and the tooth curve inward, and thus the alse and 

 the tooth turn concave sides towards each other. The tooth is generally a little narrower than the 

 alse together, and sometimes of the same length, sometimes a little shorter; it forms an acute angle 

 with the shaft. The tuberculum is longish, and a rather inconsiderable falx is found. This chela 

 may vary somewhat as to form, especially with regard to the breadth of the alse and the tooth, and 

 the length of the middle part of the shaft; also the end of the tooth may be differently rounded, and 

 the lower edge of the alse may join the shaft at a right angle or with an even curve. The length is 

 generally between 0-078 and o-092 mm , but a few smaller ones occur, down to o-05 mm . The greatest breadth 

 is most frequently 0021 — o - o28 mm , but much narrower forms may be found. Also of this chela a few 

 developmental forms were found; they are very like those of the preceding form, from which they 

 may be especially distinguished by the fact that a falx is begun at an earl}' stage. The incipient alse 

 are as to form somewhat different from the fully developed ones (PL VIII, fig. 1 f|, but the final form is 

 reached through mere apposition. 3. The third form of chelse is considerably smaller than the pre- 

 ceding ones; these chelse are of a form similar to that of the middle ones, but their shaft is somewhat 

 curved; the breadth of the teeth is the same as that of the alse taken together. The length is between 

 . 02I mm anc i o^i™'", only rarely towards the latter length, the breadth is 0-0057 — o-oo7 mm . A few chelee 

 may be found, seeming by their size and by having only a slightly curved shaft to form a transition 

 between the two latter forms. Carter, as may be seen from his description and figures, has seen all 

 three forms of chelse, but on account of his interpretation of the growth of the chelse he has taken 

 the smallest and middle forms to be developmental stages of the largest form. What Topsent I.e. 

 says of the largest chela?: Pour realiser leur form, ces isocheles subissent une atropine a pen pres 

 complete de leur dents laterales» is not correct; these chelse, as the other chelse in the sponge, and 

 as all palmate chelse, have distinct alse on the shaft (Topsent's dents laterales), but these are nar- 

 row and their lateral edges are parallel. 4. Sigmata; they reach a more considerable size than is 

 commonly the case, and in this respect they are exceedingly varying; they are of the common sigma- 

 form, sometimes a little irregular, and their form may be somewhat varying, they may also be plane 

 or contorted to some extent, mostly only to a slight degree. The length varies from o-ic) mm down to 

 o-o45 mm , and the thickness varies in proportion from o-on mm to ooo2 mm . Monstrous forms of sigmata 

 may occur, and especially one form is not rarely seen, in which one end is split into two or more 

 points, as figured by Fristedt I.e. fig. 39. Besides sigmata are found quite singly some bodies which 

 I must suppose to be developmental forms of sigmata; they are curved like the axis of a sigma, and 

 the ends are tapering, but they are quite, or to a higher or smaller degree, wanting the recurved ends. 

 They have been measured of lengths from 0-058 — o-i8' nm with thicknesses from o - ooi— o-oo25 m,n . Thus 

 this sigma seems to reach a considerable thickness, before its ends are properly developed. 



Embryos. In some of the specimens embryos were found scattered in the body of the sponge, 

 sometimes singly, sometimes several ones together. They were roundish, of a diameter of about i mm . 

 Their spiculation shows some peculiarities. Of megasclera they have very fine styli, generally with 



