76 Rev. T. Hincks on the Reproduction 0/ Clavatella, 



The number of the tentacles is constant in the sexual zooid, 

 always amounting to six. The internal structure is curious, and 

 closely resembles in part that which has been described by Dr. 

 Strethill Wright as occurring in Coryne and Stauridia (Edinb. 

 New Phil. Journ, for April 1858). The tentacles in these 

 genera, he says, " are not hollow, but contain a core or chain of 

 endodermic cells, placed in single series. The contents of each 

 of these cells consist of highly vacuolated sarcode, which includes 

 a nucleus, accompanied by a few coloured granules, the function 

 of which has not been determined.^'' The central chain of cells 

 is very apparent in the arm of the Clavatella-zooid, and down 

 the middle of it there runs a line of coloured granules (brownish) 

 (PI. VIII. fig. ^). 



Another portion of the structure of the arms I find it difficult 

 to explain. From certain points on the median line of granules, 

 threads pass off on each side to the cell-walls, or rather, perhaps, 

 to longitudinal muscular bands traversing the length of the ten- 

 tacle (PI. VIII. fig. </). M. de Quatrefages has described a simi- 

 lar structure as occurring in his Eleutheria, in a ' Memoire ' to 

 which I shall have occasion to refer more particularly hereafter, 

 and he connects it with the muscular system *. The muscular 

 energy of the arm is very great, as evidenced by its percussive 

 action, its contractility, and its vigorous locomotive power. 



The ectoderm appears to consist of a series of cells, somewhat 

 semicircular in form, in which I have often observed a small 

 nucleus, which may possibly be connected with a " palpocil " 

 {vide Dr. Wright^s paper ut ant.), though I have not succeeded 

 in detecting any such organ. 



The shorter branches of the arm terminate in a somewhat 

 funnel-shaped opening, which is closed below by the core of 

 endodermal cells. They have very considerable adhesive power, 

 and constitute efficient organs of locomotion. 



When the zooid approaches its full development, its move- 

 ments become frequent and vigorous, and at length the pedicle 

 by which it is attached gives way, and it enters upon a period 

 of free existence, during which the generative products are ma- 

 tured and discharged (PI. VIII. fig. 3). It now moves about, 

 with the proximal portion of the body uppermost, using its 



* The following is the passage referred to : — " Dans I'interieur dii tenta- 

 cule, on trouve un appareil fort singulier, dont il n'est pas facile de donner 

 une idee exacte ; c'est line esjiece de charpente, composee d'un axe irregu- 

 lierement coude en zigzag, dont chaque angle porte une bvanche, qui va 

 se fixer a I'une des bandes niusculaires longitudinales des parois. Ces 



branches et I'axe lui-merae sont eminemment contractiles N'hesitons 



nous pas a les regarder comme etant de nature musculaire, et comme desti- 

 nees a movivoir les bras dans toutes les directions." 



