368 DR W. CARMICHAEL M'lNTOSH ON THE STRUCTURE OF THE 



tracted with force, so as to propel the granules, and even the glandular lining of 

 the cavity itself, forwards to the front of the basal sac. The superficial granular 

 glands of the stylet- region are also well developed. 



Some weeks afterwards (and there was no difficulty in preserving them for 

 this period, even without a change of water) four eyes were observed in the ma- 

 jority. The head of the worm is distinctly marked in crawling, and the cuticle 

 richly ciliated, a few longer cilia occurring at the snout and tail. Ciliation is also 

 very active in the cephalic pits, whose openings are circular; and there is, moreover, 

 a slight constriction at this point between the two pairs of eyes. The dermal 

 tissues are well seen, and the ganglia are still relatively large. Every structure 

 pertaining to the proboscis now shows considerable advancement; and it may be 

 noted that the posterior glandular organ is wider and shorter in proportion than in 

 the adult. In each lateral stylet-sac (Plate IX. fig. 13) there are at least three well- 

 developed stylets, whose heads still appear somewhat more globular than in the 

 perfect animal, besides a headless fragment or two. and one or two clear globules. 

 The normal position of these organs in the lateral pouches seems to be transverse. 

 The stylet on the central apparatus is completely formed, and likewise has a 

 somewhat globular head. The muscular cavity (e) is kept in constant jerking 

 contractions under pressure, while the posterior part {6) is quite still. The other 

 structures, such as the cells of the digestive cavity, had made corresponding 

 advancement, but no blood-vessels were apparent. It may be mentioned, in 

 passing, that the cuticular tissues of these domesticated examples become less 

 transparent than in the wild forms brought from the rocks, and the examination 

 of the internal organs is consequently interfered with. In these young animals 

 also (under pressure) the proboscis generally escaped by rupture at the posterior 

 end, as in Tetrastemma variegatum, probably by passing through the anus. In 

 the adult protrusion rarely occurs posteriorly, but almost invariably anteriorly. 



The ova of 0. gracilis (Plate VIII. fig. 9) are much smaller than those of O.alba, 

 and when first deposited adhere together slightly, so that they may be pushed en 

 masse, but they afterwards lie flatly on the bottom of the vessel. Each likewise 

 possesses two coats. The vitellus is of a dull yellow hue. Though there is no 

 doubt the spermatozoa in this, as in other species, rapidly diffuse themselves 

 throughout a large bulk of water, yet they were applied directly to the ova by 

 means of a pipette. In about four hours many were adhering to the exterior of 

 the hyaline coat, others were within this, while a few seemed to have penetrated 

 both capsules (Plate VIII. fig. 10). In six hours cleavage had proceeded much 

 farther, so as to cause many to have the usual mulberry-aspect. In O.pulchra the 

 contents of the ovaries are of a beautiful rose-red colour, with a clear spot in the 

 centre. Each ovisac in the middle of the body contains from twelve to twenty ova, 

 therefore it is unlikely that this is a viviparous species, unless only a single ovum 

 happened to be detained in an ovisac here and there, impregnated and developed. 



