362 LIVERPOOL MARINE BIOLOGY COMMITTEE REPORT. 



the horns of the dorsal tubercle was found to bifurcate, a 

 condition which has apparently not been previously noticed. 



Some Ascidians vary greatly in the amount, the position, 

 and the colours of their pigmentation. Ascidia scabra and 

 Ascidia virginea may be mentioned as being particularly 

 variable in this respect. I have recently examined a large 

 number of specimens of Ciona intestinalis, in the living con- 

 dition, from the Isle of Man and other parts of the west 

 coast, with the view of determining what amount of variation 

 exists in regard to the two conspicuous red pigment spots 

 placed in that species near the anterior end of the body, one 

 on the dorsal and the other on the ventral edge (see PI. IX. 

 fig. 7) of the branchial sac. 



The dorsal pigment spot (PI. IX. fig. 7, and fig. 9, 

 d, p.) is a rounded mass placed on the outer {i,e. dorsal and 

 anterior) surface of the nerve ganglion ; it must not be con- 

 fused with the pigmented glandular mass of the same colour 

 placed a little further back, upon the anterior extremity of 

 the vas deferens, and which is regarded by Koule * as a 

 renal organ. The ventral pigment spot (PL IX. fig. 7, and 

 fig. 10, V. p.) is a mass of crescentic form which curves 

 round the anterior extremity of the endostyle, in front of the 

 peripharyngeal bands (PL IX. fig. 10, v,p,). 



After noticing these red spots in many specimens of 

 Ciona intestinalis, it was natural to conclude that they are 

 always present in the species, and consequently, I was rather 

 astonished to find that amongst half a dozen specimens, 

 living in a small aquarium, two had no pigment spots at the 

 anterior end of the body. I then examined, in the fully 

 expanded condition, every specimen ot Ciona intestinalis 

 which I dredged until one hundred and fifty had been col- 

 lected. This series shewed that the four possible variations 

 in regard to the pigment spots — viz., with both spots present, 



* Eecherches sur les Ascidies Simples des Cotes de Provence, p. 170. 1884. 



