130 Proccedinys of ike Royal Society of Victoria. 



track wliicli viiider ordinary circumstances the animal leaves 

 behind it wlien it crawls, only in the latter case the secretion 

 of slime, and consequently the slimy track, are continuous. 

 1 do not mean to suggest by this comparison that the 

 gelatinous matrix is identical witli the ordinary slime, for 

 that I think highly impi-obable. 



With regai'd to the development of the eggs my observa- 

 tions have been attended with very little success. The 

 o))acity of the embryos, due to the pi'esence of a large 

 quantity of food yolk, renders investigation of them in the 

 living state extremely difficult, and the cutting of sections, 

 which I also attempted, has not so far yielded satisfactory 

 results either. As might have been expected, I have not 

 foimd any ti'ace of the Pilidium stage so characteristic of 

 some marine nemertines. 80 far as I can judge at present 

 the development appears to be direct. 



On August Sfith I examined some of tlie embiyos from 

 the mass of eggs which was found freshl)' deposited in the 

 vivarium on August 1st. It was easy to distinguish, two 

 stages of development. In the first the embrj-os were 

 spherical and eacli enclosed in a very delicate transparent 

 membrane. Each was about 0'6 mm. in diameter, opaque and 

 solid-looking, and clothed with short cilia. They revolved 

 slowly inside their delicate envelopes and sometimes slightly 

 changed their shape. In tlie second stage the embryos had 

 emerged from their delicate envelopes and under the 

 microscope they slowly crawled about, constantly changing 

 their shape in an amoeboid fashion, elongating as they crawled. 

 They were clothed with short cilia and were still perfectlj' 

 opaque. No eye spots were yet visible. 



The next stage observed was in the mass of eggs collected 

 by Mr. Fiddian at Creswick, some of which I examined on 

 August 26th, about a month after they had been found. 

 When removed from the soft, investing jelly these embryos 

 elongated themselves greatly and crawled about pretty 

 freely, much after the fashion of the adult worm. A single 

 pair of eye s|)ots was visible at the anterior end. Micro- 

 scopic examination, by means of sections and otherwise, 

 showed that the proboscis, alimentary canal and nervous 

 system were all well developed, even the characteristic 

 stylets of the proboBcis being present. Hence, although these 

 animals had not yet left the investing jelly, the development 

 was nearly complete. The alimentary canal still contained, 

 however, a ver}^ large quantity of unabsorbed yolk-granules. 



