142 W. M. Bale: 



(ionosome 1 



Cdlour, blown (" fauve Ijiillant et fonce '" — Lainouroux). 



Ilah. — Mer des Antilles (Laniouroux) : Algoa Bay and Algieis 

 ((Krauss) : Fort Dauphin, Madagascar (Billard) : Cape of Good 

 Hope (Kirchenpauer). 



This African species, which is not known to occur in Australia, 

 is introduced here on account of Billard's having referred to it our 

 M. ascidioides, which indeed singularly resembles it in several jDar- 

 .ticulars, but which, as I shall show, is nevertheless quite distinct. 



The form which is described above (from specimens obligingly 

 forwarded to me by Dr. Stechow fi'om the Munich Museum) is. I 

 have no doubt, the true Aglitoplienla arcuata of Lamouioux and 

 Kirchenpauer (also the Halicornaria cornuta of Allman), but Billard 

 includes with it several forms which he considers to be the young 

 •colonies, and which, if really to be referred to the same s^Decies. 

 stamp it as variable to an extent unknown elsewhere in the order. 

 I have not seen these forms, some of which appear scarcely to differ 

 from our //. longirostris, and the specimens sent to me, which 

 include young colonies of only two centimetres in height and mature 

 ones of eleven or twelve, do not differ noticeably among themselves. 

 When the mesial sarcotheca is carried forward parallel with the 

 hydrocladium they agiee }-oughly Avith Lamouroux' figure, when it 

 is more oblique they approximate to Kirchenpauer's. 



According to Lamouroux' figure the hydrocaulus is dichotomously 

 ■divided several times, but from Billard's account the ramification 

 is peculiar and probably unique ; a branch springs from the front 

 of the hydrocaulus, and has its anterior aspect directed towards 

 that of the stem, and each successive branch grows in the same 

 manner. The result of this mode of branching appears to be that 

 all the branches are in one plane, but in a plane at right angles to 

 that of the hydrocladia. This may l)e contrasted with the condition 

 which prevails in //. furcota and its allies, where the hydrocaulus 

 bifurcates in a single plane, which is also the plane of the hydio- 

 cladia. According to Lamouroux' figure the l)ranches diverge at a 

 Tery wide angle (about 90 deg.). 



Billard states that in young colonies the cauline intoinodes are 

 longer than wide, and nearly cylindrical, while in mature colonies 

 the side of the internode on which the hydrocladium is borne is 

 about double the length of the opposite side. The latter description 

 applies to all my specimens, young and old, except that the differ- 

 ence in length of the two sides is not so gi-eat. Tlie intt-i'iiodes arc 



