604 P. HEKBEET CARPENTER. 



pigment-bodies, which are so familiar to all workers on 

 Echinoderms. 



Koehler makes little reference to the observations of Geddes,^ 

 who found amoeboid corpuscles containing brown pigment - 

 granules in the perivisceral fluid, and considered them as 

 respiratory in character. These cannot be very difi"erent from 

 the pigmented '' cellules a protoplasma irregulier emettant de 

 fins prolongements," which Koehler found in his osmic-acid 

 preparations of the ovoid gland ; while the larger pigment 

 masses, devoid of a nucleus but surrounded by a thin proto- 

 plasmic envelope, which Koehler found in the ovoid gland, 

 seem to have been also met with by Geddes in the intestinal 

 vessels. He also describes them as occurring at certain times 

 in the ambulacral vesicles ; and he speaks of these yellow-brown 

 granules as being developed at the expense of the nuclei of their 

 epithelial lining, which recalls the relation of similar granules 

 to the nuclei of cells derived from the epithelium of the so- 

 called glandular canal described by Koehler. The Polian vesicles 

 have essentially the same structure as the " ovoid gland/' and 

 are evidently the source of many of these pigmented cells. The 

 colouring matter of the latter contains iron, and undergoes 

 changes of tint when exposed to the atmosphere, so that it is 

 doubtless of a respiratory nature, as supposed by Geddes, 

 though Foettinger's discovery^ of hsemoglobin-tinted cor- 

 puscles within the water-vessels must not be forgotten. 



Considering that the production of these pigment granules 

 involves the destruction of the cells of the ovoid gland and 

 Polian vesicles, Koehler regards these organs as excretory in 

 function, as had been previously done by those who denied the 

 connection of the ovoid gland with the vascular system, though 

 positively asserting its communication with the exterior by a 

 duct. It is likely enough that this organ is one of the facto- 

 ries of respiratory pigment, the necessary material reaching it 



' "Observations sur le lluidc perivisceral dcs Oursins," ' Arcb. de zool. 

 exp. ct. gen., t. viii, pp. 483— iUG, pis. xxxvii, xxxviii. 



" "Sur rexistcnce do rhciiioglobiiie cbcz ics Ecliinodermes," 'Arcli. de 

 Biol.,' vol. i, pp. -1U5— 112, pi. xvii 



