60 A. C. WALTON 



and two days during which it was under observation. It how- 

 ever did complete the formation of two separate diglyphic 

 mouths, thus giving further evidence of the progressive nature 

 of the development of double forms of A. bermudensis. 



When found, the mouth was triglyphic, i.e., it was roughly 

 triangular in shape, with the basal side deeply indented, and 

 having a siphonoglyph at each angle. The tentacles were one 

 hundred and thirty-one in number when the animal was found, 

 and had increased to one hundred and fifty-three when it was 

 killed and dissected. The complete, and many of the incom- 

 plete, mesenteries (fig. 6) could be seen through the transparent 

 oral disc. From two of the siphonoglyphs extended paired 

 directives, while from the third or ' apical' one there appeared to 

 be three mesenteries extending to the column wall. Between 

 the divided siphonoglyphs were two non-directives, one to each 

 half of the mouth (fig. 6). Between the siphonoglyphs at the 

 basal angles of the roughly triangular mouth, and the one at the 

 apex, there were five pairs of non-directives on each side of the 

 animal.^ Between the adjacent pair of complete mesenteries 

 could be seen traces of from one to three pairs of incomplete 

 septa (only one pair is indicated in the diagram). In all, twenty- 

 four paired and five unpaired complete mesenteries were present. 



By the end of the fourth week of observation, the animal had 

 formed two entirely separate, diglyphic mouths, and had in- 

 creased the number of tentacles to one hundred and fifty-three. 

 As want of time did not permit further observation, the animal 

 was killed and dissected. The two mouth openings were en- 

 tirely separate, but the two oesophageal tubes were not so, 

 being united at their extreme buccal ends, and opening into the 

 gastro vascular cavity through a common orifice ; the four siphono- 



^ Figure 6 reproduces the conditions as they were observed in the living ani- 

 mal through the thin-walled oral disc, and represents the right half of the ani- 

 mal as containing 6, instead of 5, complete non-directive pairs of mesenteries. 

 Sections of the later stage of this animal made subsequently (figs. 7 and 8) show 

 that a mistake was probably made in sketching the mesenteries of the right side; 

 for in this later stage only 5 such mesenteries are to be found; the possibility of 

 error in counting the mesenteries in the living condition is considerable, but not 

 so in the sections. 



