PORIFERA. II. 40, 



possible to state their form exactly. When the chela is viewed with the smaller end turned directly 

 towards the beholder, however, the alae and the tooth are distinctly seen together with the part of 

 the axis between them (PI. X, fig. 4I1). These chelae are very small, their length is o-oio— o-oi 14""", 

 and the breadth is 0-0057™™. 2. The large anisochelse are of a peculiar structure not quite easily 

 understood. The shaft is about straight. The two ends are very different; the larger one is of the 

 common Myca /^-structure, the alae are much refolded on the side, and the tooth is considerably nar- 

 rower than the alae; a rather long tuberculum is found pointed downward. The form of this end is 

 rather constant in one individual, but may be somewhat varying in different individuals. The variation 

 consists in this end becoming longer in proportion to the total length, the lower edge of the alae 

 bending much downward on their way outward from the shaft so as to form a far out-drawn lower 

 corner, and the tooth becoming longer and at the same time narrower. The alae and the tooth may 

 get so great a length as to reach the structures from the lower end of the chela. The smaller end 

 of the chela is of a peculiar structure and shows a remarkable irregularity. When the chela is viewed 

 from the front or from the side, some small teeth appear to issue from the lower end. Only when the 

 chela is placed with the small end turned towards the beholder, it is possible to get a clear view of 

 the structure. The shaft is then seen to have a narrow ala on either side; next three laps or teeths 

 are generallv seen below, one on either side and one in the middle. The middle one is either un- 

 divided or more or less split in two; most frequently it is completely divided, and then we get alto- 

 gether four laps. This is the construction when it is regular, but frequently it is irregular and 

 unsymmetiical, so that we see two laps on one side and only one on the other, or the two laps of 

 the middle tooth are of unequal size. Also the alse of the shaft may be unsymmetrical, as upon the 

 whole this end is subject to much variation. The laps or teeth are so thin and transparent, that, 

 when the chela is not seen from the end, they are hardly to be observed. Unfortunately I have found 

 no developmental stages of this chela, and so it is impossible to ascertain how the construction of the 

 smaller end is to be interpreted, whether we have here real teeth, or one tooth divided into laps, or 

 finally the lateral teeth are to be interpreted as belonging to the alas of the shaft. When two teeth 

 are found in the middle this is surely the result of cleavage, which may also be seen from the fact 

 that in such cases we find a median tuberculum the upper part of which is split. Also the lateral 

 teeth seem to be provided with a tuberculum, but by this fact it is not proved, however, that they 

 are independent teeth. Perhaps the developmental forms may solve this question. The length of the 

 chela is between 0-048 and 0-063™™, tne greatest breadth is 0-022—0-027™™, and the thickness of the 

 shaft is ca. o-oo4' n ™. As the length is proportionate to the mentioned variation in the form of the 

 upper part, it is rather constant in one individual. The longer the upper end is in proportion to the 

 total length, the shorter is the chela. 3. Sigmata; they have a comparatively little curved shaft, 

 while the tolerably short ends are strongly bent in a hook-like way. A peculiar feature is that the 

 shaft towards the bendings is compressed, and therefore a little broader, seen from the side. They 

 are contort, most frequently a quarter of a turning, and they may therefore, by a slight glance and 

 under small magnifying powers, recall small tylostyli, as observed by Schmidt I.e. That they may 

 appear as tylostyles arises from the fact that the hook which is turned upward is not seen as a hook, 

 but may give the impression of a swelling. Their length is o - 02i — 0-024™™, a "d tne thickness about 



The Ingolf-Expedition. VI. j. n 



