128 Dr Grant's Observations on the Structure 



periments ; to observe the animal at all seasons of the year ; and 

 to confirm my observations, by various continental authorities 

 which were unknown to me when my experiments were first 

 read before the Wernerian Society. During the months of Oc- 

 tober and November, we observe a remarkable change taking 

 place in the internal texture of the ♦S'. panicea, the parts which 

 in summer were transparent, and nearly colourless, have now be- 

 come every where studded with opaque yellow spots visible to 

 the naked eye, and without any definite form, size, or distribu- 

 tion, excepting that they are most abundant in the deeper parts 

 of the sponge, and are seldom observable at the surface. The 

 parenchymatous matter seems likewise to be more abundant 

 throughout the whole body. By examining thin sections with 

 the microscope at this period, we find that the bright yellow 

 spots consist of groups of very minute irregular-shaped gelati- 

 nous granuleSjWhich lie imbedded in the parenchymatous matter, 

 and are contained in certain recesses formed between the parie- 

 tes of the internal canals^ (fig. 26, b.) These yellow granules 

 are the rudiments of the ova, and when they are first perceptible 

 by the aid of the microscope, they consist only of a small round 

 compact group of the same monade-like bodies which compose 

 the parenchymatous matter ; they have no cell or capsule, and ap- 

 pear to enlarge by the mere juxtaposition of the monade-like 

 bodies around them. As they enlarge in size they become oval 

 shaped, and at length in their mature state they acquire a regu- 

 lar ovate form. In about two months after their first appear- 

 ance, the ova are nearly a fifth of a line in length, and half as 

 much in breadth, and the greater number of them have acquir- 

 ed the same ovate form and bright yellow colour. Their form 

 is now quite distinguishable by the naked eye, both when floating 

 detached in water, (above fig. 26,), and when lying in groups in 

 the substance of the animal, (fig. 21. J', f-)- Before they ha\e 

 attained this perfect ovate form, they are not washed out from 

 broken sponge, by violently shaking it in water, but now they 

 readily fall out from broken portions, without any agitation, and 

 we generally find a great number of them floating in the water 

 in which specimens of this sponge have been placed in the months 

 of December, January, February, and March. If we watch 

 the fecal orifices with some attention during any of these months 



