REPORT ON THE ACTINIARIA. 73 



and its external appearance presented so little that was characteristic, that I gave up the 

 idea of determining the species more closely, and only decided to give a description of it 

 in order that the important genus might not be left unrepresented. 



The animal was so strongly contracted that its body formed a cone, nearly flattened 

 into a disk, the base of which measured 4 cm., whUst its height measured little more than 

 0"5 cm. The surface of the animal is extremely smooth ; it is whitish at the base, 

 then assumes a yellowish-reddish colour, which again passes gradually into white. The 

 coloured part appears longitudinally striated, because the red and yellow alternately 

 predominate in the ground-tint. 



The wall is on the whole thin-membraned, and becomes about six times as thick 

 only at the upper margin. This very unusual increase in bulk is explained partly by 

 the high degree of contraction, partly by the great strength of the mesodermal circular 

 muscle. The latter occupies nearly the entire thickness of the wall, and is only separated 

 from the ectoderm by a very thin layer of connective substance, whUst a rather broader 

 layer separates it from the endoderm. Its contour corresponds to the form of the wall, so 

 that it is broad above and drawn out to a point below. We rarely find such beautiful 

 primitive bundles in transverse section as in our Sagartia ; they are formed of strong 

 fibrHlse, are regularly oval or rounded circularly, and of medium size. On the other 

 hand, the way in which they run is remarkably irregular. In the same transverse 

 section we find, side by side, bundles, some divided obliquely, and others divided perpen- 

 dicularly, and we see in the thicker parts of the section how the bundles cross and become 

 interwoven in their course. 



Contrasted with the circular muscle, the radial muscular fibres of the oral disk and of 

 the tentacles are only slightly developed, and form a very slightly pleated layer in the 

 ectoderm. The tentacles are limited to the periphery of the oral disk, where they are 

 arranged in five rows, and decrease a little in size from within outwards. They are 

 of medium length, rather slender, and pointed at the end. I counted twenty-five in about 

 an eighth of the animal, so that there are probably one hundred and ninety-six in aU. 



From transverse sections taken through the oesophagus I estimated the number of 

 septa at forty-eight pairs, of which the six principal pairs only are perfect. There 

 would probably be a much larger number at the base, as small septa reaching only a 

 little way project there, in the angle between the pedal disk and the wall. There were 

 reproductive organs (mature testes) on all the larger secondary septa. Finally, in 

 transverse section, I could perceive wide openings in the septa near the wall. 



Calliactis, Verrill. 



Sagartidae with smooth wall and numerous tentacles, with distinct cinclides which 

 pierce the waU not far from the base in one or several transverse rows. 



(ZOOL. CHALL. EXP. — PART XV. — 1882.) p JQ 



