214 



PORIFERA. II. 



as mentioned, ma}- be varying, but is always short; from a distinct point, bounded by straight lines, 

 but short, all transitions are found through shorter and more stubby forms to a broad rounding of the 

 pointed end. In this respect there may be some difference in different individuals; in some, and 

 perhaps in most, styli with quite rounded end are rare, while in a few specimens thev are most 

 numerous. Their length varies from cr68 — o-86 mra , and the thickness from 0-014 — o-o2i mm , in some indi- 

 viduals they scarcely reach this thickness. A few developmental forms occurred, the finest ones are 

 all pointed, but they may be rounded already when rather thin. 2. The dermal spicules are 

 tylota with very slightly swollen ends; not rarely almost no swelling is found, so that thev become 

 strongyla; they are straight or quite slightly fusiform. Their length may be rather varying, from 

 041— o-62 mm , not varying so much, however, in one individual, the thickness is ca. 0-008—0-0 i7 mm . The 

 developed tylota have equal, or about equal ends, but a few quite fine forms were found, indicating 

 that they are begun as monactinal. b. Microsclera are sphserancorse and ancorse spatuliferae of two 

 sizes. 1. The sphserancorse are the wellknown ancorse described by Carter as «melon-shaped 

 anchorates*. Carter supposed the common ancorse to be developmental forms of the sphserancorse, 

 which was in accordance with his general view of the growth of these bodies. Levin sen (Vidensk. 

 Meddel. fra Nat. For. Kobenhavn for 1893, 1894, 13 seq. Tab. I, Fig. 31—49) has already pointed out the 

 error in this view, and he is the only author, who has given a complete, and, apart from a single 

 mistake, correct description of the sphserancorse and their mode of growth. The sphseraucora consists 

 of four arcs, connected with each other at the ends, and forming right angles with each other, so 

 that they form an ellipsoidal body. Each of the arcs consists of a principal part or axis and of a 

 thin plate-shaped brim issuing from the outward-turned dorsal side of this axis; this brim folds round 

 on eiter side of the axis and lies as a thin plate on either side of it; it is of about the same breadth 

 as the axis of the arc, and it is seen to be finely and transversely striated. The sphserancorse are 

 typical ancorse, as is shown by their development. The youngest stage observed consists of a 

 thin shaft with three thin, rather long beginnings of teeth at each end; in contradistinction to 

 the common ancorse no falx is developed here. The teeth now become longer during the growth, 

 and at the same time both they and the shaft become broader in the radiate direction; finally the 

 ends of the teeth meet and coalesce, and the body that was begun as an ancora, consists now of 

 four narrow arcs whose ends are joined, or of two ellipses intersecting each other at a right angle. 

 The body now formed consists only of the middle or axial parts of the arcs, and as yet no striation 

 is seen; in older stages the striation is seen to begin first along the dorsal side of the arc, but 

 reaching by degrees farther inward, until the striated lateral plates or brims are formed in their 

 full breadth, and the sphserancora is complete. The striated brims correspond completely to the 

 alse and tooth-plates of a common ancora. Strictly spoken, the term striated brims or plates is 

 not quite correct, as it is seen distinctly by sufficient enlargement that the question is not of a brim 

 with strise, but, on the contrary, of a series of close-standing, fine teeth; in developmental forms with 

 beginning brims it is seen especially distinctly that the teeth are free, later they become a little 

 broader, and then they adjoin, each other closely, only their somewhat pointed end is then seen to be 

 free. When the ancora is full}- developed, the four arcs are quite equal; it may, however, generally 

 be decided, which of the arcs is the original axis; on the three arcs formed by the coalesced teeth, 



