IOO PORIFERA. II. 



When all sizes are included, the length is between 0-417 — o-8o mm , and the thickness is 0-014 — o-025 mm 

 For the needles of the axes the length ma)- be given as being generally 0-417 — o-6 rem , and for the 

 needles in tissue and branchlets ca. 0-55 — o-8o ram , and the thickness is rarely more than o-02i' nm . Some- 

 times this difference is less marked, and it is especially found in the upper and outer ramifications, 

 while down in the sponge and in the stems and the thicker branches it is more effaced. In the tissue 

 fine, long pointed developmental forms are seen singly, b. Microsclcra; these are anisancorse unguiferse 

 and sigmata of two forms, larger ones and smaller ones. 1. The an corse are of the common Clado- 

 rhiza-iorm; they have a curved shaft and rather broad alae at the larger end. The}- have five teeth 

 at either end, but forms with six teeth at the larger end are also found. The length varies from 

 0-026— o-034 mm , and the thickness of the shaft from 0-0028— o-oo35 mm . Developmental forms of the 

 ancorae are found in small numbers. 2. The large sigma has a regular sigma-form; these sigmata 

 are plane or almost plane; the length is 0-09 — o-i2 ,nm , in by far most cases nearest to the latter length, 

 the thickness is 0-0057 — 0-007™™. Developmental forms in different stages were seen in no small 

 numbers. These developmental forms are distinctly seen not to be cylindrical, but sharpened inward 

 from a little over the middle and to the ends; this feature, on the other hand, is not to be seen in 

 the fully developed sigmata. 3. The small sigma is only found in the end of the branches, and 

 is of the same form, with inwardly sharpened terminal parts, as the sigma occurring in the same way 

 in the preceding species. It is likewise contort, almost always a fourth part of a turning. The length 

 is 0-047 — o-054 mm , and the thickness in the middle of the shaft about o-oo2 m:n . The ancorae and the 

 large sigma occur partly throughout the tissue and partly in the dermal layer, especially the ancorae 

 are abundantly present in the outermost layer of the branchlets. The small sigma only occurs in the 

 point of the branches and not in all of them, but only in those that are distinctly swollen; here it is 

 found abundantly. On the other hand, the large sigma is here only seen quite singly. 



Embryos. Embryos were also in this species found rather copiously in the tissue. They are 

 roundish or most frequently oval, and they are surrounded by a thin membrane. Their size is about 

 j mm By the examination they proved to be either without spicules, or only provided with develop- 

 mental forms of the ancorae, but these were found rather copiously. The developmental forms were 

 mostly rather young stages, they had a length of 0-024— °'° 2 7 mm i or about the same length as the 

 ancorae of the grown sponge. The embryos are situated in the tissue outside the axes, they are fre- 

 quently found at the base of the branchlets, or in this base itself; in a few cases they are seen out 

 in the middle of the branchlets (Woodcut, Fig. 6). According to this I suppose that they leave the 

 sponge by this way, and so we are again led to regard the branchlets as oscula. I have, however, 

 not been able to find any canal, and accordingly, if such a one is found, it must be supposed to be 

 closed. The fibre of the branchlet is almost always found in one side, and the canal must be supposed 

 to run alongside of it. Also the embryo is placed in one side of the branchlet beside the fibre; it 

 distends the branchlets in the middle, and on the sides where the fibre is not found, it is surrounded 

 by a thin membrane only filled with microsclera. It is to be remembered, however, that the occurrence 

 of the embryos in the branchlets may also be supposed to be owing to the fact that they develop here 

 as in other places in the sponge. 



The figure presented by a branchlet with an embryo in it, involuntarily directs the thought 



