47-i K. KAMUNNl MENON. 



The metamorpliosis of the larva is usually completed iu a 

 few minutes. Occasionally, however, the ventral diverticulum 

 is evaginated, and it is only after a considei'able interval that 

 the alimentary canal is drawn into it — the animal then pre- 

 senting a curious external resemblance to Rhabdopleura, as 

 far as one can conceive of it from figures. The young 

 Phoronis fixes itself to tbe bottom of the glass vessel by 

 means of a sticky secretioUj and also secretes a transparent 

 cuticular tube round the body. Observation of the living 

 animal shows that the annulation of the body, said to be due 

 to contraction in spirit, is quite natural. These annuli are 

 formed by the ectoderm being raised up into ridges. If the 

 water in which they are kept is not changed daily, the young 

 animals lose their heads — a fact in agreement with Cori's 

 observation that the tentacle crown is often thrown off by 

 Phoronis, especially under unfavourable conditions. 



Epistome. — This structure is usually regarded as a 

 remnant of the preoral lobe of the larva. In the young 

 Phoronis, soon after metamorpliosis, the epistome is not 

 present. The preoral lobe and the tentacles of the larva are 

 apparently wholly taken into the alimentary canal during the 

 metamorphosis. In the case of slow metamorphosis these 

 persist for a compai-atively long time, and tbeir disappear- 

 ance must be due to disintegration. In the young Phoronis 

 the dorsal part of the region surrounding the mouth and 

 immediately within the ring of tentacles is raised up into a 

 round protuberance (fig. 1). This is the beginning of the 

 epistome. The collar cavity, which was encroached upon by 

 the masses of blood-corpuscles in the old Actinotrocha, does 

 not extend into this swelling, the interior of which is occupied 

 by a nucleated mass containing irregular spaces, and with 

 scattered muscle-fibres and blood-corpuscles. The surface 

 epithelium does not differ from that covering the rest of the 

 oral region. The papilla gradually becomes flattened out 

 into a broad flap (figs, 2 — 4), having a thick base attached 

 along the dorsal edge of the mouth, and a thin free edge. 

 The internal mass is absorbed j and between the basement 



