72 



MR JAMES RITCHIE : SUPPLEMENTARY REPORT ON 



what is probably part of the main stem, and with a height of 1'^ cm. It bears rather 

 delicate alternate ramuli which leave it almost at right angles. 



AVhile the general characters — branching, structure of hydoclades, shape and 

 approximation of hydrothecse, position of nematophores — agree with the descriptions of 

 Allman (1877, p. 39, pi. xxiii.,as^. ramosa) and of Nutting, variations worthy of note 

 have been observed in the last-mentioned organs. These variations seem to be mainly 

 age differences. In the hydrothecse on the proximal parts of the hydroclades the mesial 

 nematophore reaches to the level of the marginal teeth, and is adnate, all but the very 

 tip. The supracalycine nematophores are generally cylindrical, with two apertures — 

 one terminal, the other a large oval opening on that side of the upper surface which is 



Fig. 10. — Aglaophenia nllmani, showiug variation in hydrothecse and nematotheca;. (a) Hydrothecje from tlie proximal 

 end of a hydroclade. x 65. (A) Hydrothecae from the distal end of a hydroclade. x 65. 



towards the interior of the hydrotheca. Rarely this opening is much elongated, and 

 extends through the baud of perisarc which separates it from the terminal opening. In 

 such a case a single continuous opening is formed and the nematophores might be 

 described as "almost cylindrical." The tip of a supracalycine nematophore reaches just 

 to the margin of a hydrotheca. Its axis, viewed from the side, lies at an angle of about 

 45° with the stem. The nematophores, in general, agree with the type so far described. 

 In those hydrothecae which occur towards the tip of the hydroclades, and which are 

 therefore younger, the aperture is less oblique, wdiile the adnate part of the hydrotheca 

 is of the same length as in the older examples. As a consequence the mesial 

 nematophore, although shown by measurement to be constant in length throughout the 

 colony, appears to be shorter in the newly formed hydrothecse, since its tip falls con- 

 siderably short of the margin. The supracalycine nematophores are of markedly greater 

 length, overtopping the margin by about 0'056 mm., are quite cylindrical, and lie with 

 their axis (viewed from the side) more nearly parallel to that of the internode. The 

 lateral aperture is smaller and is never continuous with the terminal one, and the 



(ROY. SOC. EDIN. TRANS., VOL. XLVII., 94.) 



