ON TtJBULARIA CROCEA IN PLYMOUTH SOUND. 55 



at intervals higher up. The annulations on the stems are neither 

 constant in position nor in number. There are usually three to five 

 sets, and the number of rings in each set varies from two to twelve, 

 but usually three or four are found together. 



The colour of the colonies showed considerable variation. At first 

 I thought the colours showed a distinction of the sexes, but further 

 examination upset this view. The colours of the different colonies may 

 be separated into two well-marked groups, the one extending from a pale 

 yellow to a dark brown, the other from a brilliant reddish brown to crimson. 

 The hydranth carries twenty to twenty-four proximal and distal tentacles. 

 The clusters or racemes of gonophores show variation in number, which 

 is chiefiy due to their not all developing at the same time. The species 

 is described with gonophores in ten to twelve pendulous racemes, which 

 are disposed in two to three rows one over the other, and which surpass 

 in length the proximal tentacles of the hydranth. To judge from the 

 specimens which I have examined, the gonophores in each row are 

 of about the same age. At first there is only one row, then follows 

 a second between the first row and the proximal tentacles, and lastly, 

 a third row on the outer side of the second row. There is apparently 

 a great difference in the age of each row, and usually only one row 

 is mature at a time. There are usually about eight racemes of gono- 

 phores, arranged in two rows ; the greatest number counted was twelve, 

 arranged in three rows. The racemes are not as long as the proximal 

 tentacles, and do not hang down as figured by Agassiz. 



A description of Tuhularia crocca is given by Allman in his mono- 

 graph on the Gymnoblastic Hydroids. 



