. The Danish Ingolf-expedition. Marine animals -- Arctic regions; Scientific expeditions; Arctic regions. PORIFERA. I. 53 The skeleton consists of a chiefly unispicular network the meshes of wliich are triangulai to put it more exactly, tetrahedral; therefore there is no question of primary or secondary fibres. The form of the ends of the spicules makes them to fit well into each other. In the nodes, in which, ac- cording to the construction of the skeleton of tetrahedral meshes, a greater number of spicules meet, these spicules are united by a very small amount of exceedingly clear spongin wh
. The Danish Ingolf-expedition. Marine animals -- Arctic regions; Scientific expeditions; Arctic regions. PORIFERA. I. 53 The skeleton consists of a chiefly unispicular network the meshes of wliich are triangulai to put it more exactly, tetrahedral; therefore there is no question of primary or secondary fibres. The form of the ends of the spicules makes them to fit well into each other. In the nodes, in which, ac- cording to the construction of the skeleton of tetrahedral meshes, a greater number of spicules meet, these spicules are united by a very small amount of exceedingly clear spongin which is difficult to observe. Spicula are spined strongyla (acanthostrongyla) of a peculiar form; they are of equal thickness in their whole length, and have rounded ends; the ends are bent rather suddenly to a more 01 high degree; they may both be bent in one direction, or in opposite directions in the same plan, and they may finally be bent in different plans. Sometimes the bending is minimal. They are set with small, scattered spines, only the ends are smooth. The length varies between 0-208—o-238mm, which agrees with the measure given by Carter, , viz. about 5°/6 inch =o-2iimm. The thickness varies between cvoio — croi2m"\ Finer spicules, developmental forms, occur in small numbers; these spicules are of interest as furnishing a distinct proof that the spicules are begun in full length; the fact is that the finest are of the same length as the fully developed ones, so that a growth only takes places as to thickness; the finest are of quite the same form as the fully developed ones, but are quite smooth, while the somewhat thicker ones begin to get quite minute spines; accordingly the spines appear first during the growth. To get a clear understanding of the growth of the spicules, it is of importance here to notice that the spicules of this species, which during the growth only increase in length to a very slight degree, are strongyla; a laying on of new parts
Size: 958px × 2608px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksu, booksubjectarcticregions
