Massy — The Gymnosomatous Pteropoda of the Coasts of Ireland. 231 



specimens of 1-2 mm. show only sixteen rows. The jaw spines are usually 

 arranged like a miniature arbour such as that illustrated by Pouchet (1870, 

 p. 278) for the construction of the Spotted Bower-Bird, Chlamydera maculata, 

 Gould. An outer palisade is sometimes present at either side of the arch. 

 The hooks always six in number, almost alike in size ; their breadth at base 

 nearly equal to their length. Specimens of 2 mm. in length usually show the 

 lateral gill, and occasionally it is just evident at a still earlier age. In some 

 specimens of 2-4 - 50 mm. the ciliated bands are absent, each being replaced by 

 a row of raised white spots ; these, when examined with a high power, seem 

 to be bladder-like, yellow, various-sized cells, with at least one aperture. The 

 smallest specimen without ciliated bands measures only 1-75 mm., and, in 

 addition to the above-mentioned rows of spots, shows a cluster of them where 

 the lateral gill would eventually appear. Some specimens of 3 mm. still 

 possess ciliated bands. In very young examples the three lobes of the foot 

 are all equal in size ; the posterior lobe rapidly lengthens with age. Tesch 

 (1904, p. 73), and recently Bonnevie (1913, pp. 67, 68), have described species 

 of Clionopsis and Pneumoderma with external genital organs. Meisenheimer 

 (1905, p. 282), with regard to Tesch's species, considers this to be due to some 

 abnormal condition. Among the present records (twelve hauls of which were 

 made in the month of November, nine in August, five in February, one in 

 May, and one in September) there are five November and four August hauls, 

 in three of which 4 per cent., in three others 25 per cent., in two 15 per cent., 

 and in one 60 per cent, of the specimens (measuring 1-2-50 mm.) exhibit 

 external accessory glands on the ventral surface of the body below the right 

 fin, and the genital duct can be seen connecting them with the internally 

 placed gonad at end of body ; the penis is evaginated above the right fin, and 

 has no outer connection with the accessory glands ; in such specimens the 

 distortion causes the head and foot to be much bent backwards. In one haul 

 nearly all the specimens showed only the right fin ; another specimen, in 

 addition to having outer accessory glands, had a second pair of fins, and a 

 second foot placed at posterior end of body on ventral surface ; there was no 

 second head, and the space below the extra foot was filled by the gonad. In 

 some examples the gonad also is external, being connected with the body by 

 a wide band which rapidly narrows, and joins the ventral surface at the right 

 side, the posterior cavity in body which usually contains the gonad being 

 found to be empty. The thin, brownish-yellow genital duct is also necessarily 

 external, and after proceeding from the pale-yellow gonad, and rapidly 

 expanding, and sometimes undulating, it narrows again before joining the 

 white muciparous and albumen glands situated ventrally ; the passage leading 

 from accessory glands to penis is not visible externally, and seems to divide 



SCIENT. PKOC. R.D.S., VOL. XV., NO. XXII. 2 P 



