26 PROTOZOA. 



the capsule, and the interval between them is filled up with a white, sili- 

 cious, amorphous matter which keeps them in position. Each spiculum 

 extends a little beyond this matter, and supports on its free end a 

 toothed disk, similar to a corresponding one on its fixed end, which rests 

 on the capsule, so that the external surface of the seed-like body is 

 studded with little stellate plates (fig. 12, d, e). In other species, where 

 there appears to be no such regular arrangement of these spicula, a 

 number of smooth spiniferous points is presented. 



(59.) If a seed-like body which has arrived at maturity be placed in 

 water, a white substance will after a few days be observed to have 

 issued from its interior, through the infundibular depression on its sur- 

 face (fig. 12, i), and to have glued it to the glass : if this be examined 

 with the microscope, its circumference will be found to consist of a 

 semitransparent material, the edge of which is notched or extended 

 into digital or tentacular prolongations, precisely similar to those of the 

 protean cell, which in progression or in polymorphism throws out parts 

 of its substance in the same way. In the semitransparent substance 

 may be observed hyaline vesicles of different sizes, contracting and 

 dilating, as well as green granules, so grouped together as almost to 

 enable the practised eye to distinguish in situ the passing forms of the 

 cells to which they belong. Subsequently to the development of this 

 fleshy substance comes that of the horny skeleton and its spicula 

 (fig. 11, 2), which are at first membranous, and at an early period of 

 their development pliable; they afterwards become firm and brittle. 

 They are hollow, and the form of their cavity corresponds with their 

 own shape ; sometimes, moreover, they contain a green matter like the 

 endochrome of the cells of Confervse*. 



(60.) In the genus Teihya, Mr. Huxley has described a true sexual 

 generation to exist, a portion of the spongy mass being found to consist 

 of a granular substance in which ova and stellate crystalline bodies are 

 imbedded. " The ova are of various sizes ; they have a very distinct 

 vitellary membrane, which contains an opake, coarsely granular yelk. 

 A clear circular space, about l ^ () O th of an inch in diameter, marking 

 the position of the germinal vesicle, is seen in each ovum, and within 

 this a vesicular germinal spot fi J^ O th of an inch in diameter is some- 

 times visible. The stellate bodies are about y^nnfth f an i ncn ^ n ^ a ~ 

 meter. The granular uniting substance is composed entirely of small 

 circular cells about . 3 ./ O th of an inch in diameter, and of spermatozoa in 

 every stage of development from those cells. The cell throws out a long 

 filament which becomes the tail of the spermatozoon, and, becoming 



* Besides the seed-like bodies above described, other reproductive bodies are met 

 with in Spongitta : 1. some which, from their resemblance to the motile spores or 

 zoospores of many plants, have also been termed swarming-spores (Schwarm- 

 sporen); and 2. others which, from their resemblance to the spermatic filaments 

 elsewhere met with, are denominated zoosperms. 



