416 Occurrence o/* Halistemma in British Waters. 



The specimen evidently belongs to the genus Halistemma, 

 but differs from all the forms of Halistemma and Agalmopsis 

 I have seen figured in the proportionally larger size of the 

 pneumatophore and the relatively greater length of the portion 

 of the nectosome between the pneumatophore and the necto- 

 calyces. The length of the specimen in its preserved condition 

 is 1\\ inch. 



Another specimen evidently belonging to the same species 

 was obtained a few days later. It measured about ^ inch in 

 length and was in a very dilapidated condition. Indeed it 

 consisted only of the nectosome with its pneumatophore, but 

 stripped of the nectocalyces and a portion of the siphosome, 

 from which all the structures had been removed. It, however, 

 showed the same relatively large size of pneumatophore which 

 characterized the other specimen. 



Note by Prof. M'Intosh. 

 The occurrence of Halistemma on the east coast of Britain 

 is of great interest; indeed, the Siphonophores are there, as a 

 rule, conspicuous by their absence. Of the other Siphono- 

 phores Dipliyes has very rarely been seen in good condition in 

 the inshore waters of Britain, perhaps the most striking 

 instance being in Lochmaddy, North Uist, in 1865, where it 

 occurred in great beauty amongst the hordes of Salpa?, 

 swimming actively through the water and avoiding the bottles 

 that were used in its capture. Amongst the Physophora 

 again Physalia is seen occasionally on the west coast of 

 England and the Outer Hebrides, very fine examples having 

 been procured off Southport in 1874. Velella is common on 

 the western shores of North Uist, and also is found in con- 

 siderable numbers at various parts of the west coast of England 

 from the extreme south northward to Scottish waters. The 

 small size of the specimens described by Mr. Sloan would 

 alone have rendered them apt to be overlooked amidst the 

 varied contents of the tow-nets. 



EXPLANATION OF PLATE XII. 



The accompanying figure is the reduction of a drawing made from the 

 preserved specimen with the aid of Ahbe's camera lucida. The objective 

 used was Zeiss's «, and the eyepiece Zeiss's no. 2. 



a. Pneumatophore. 



b. Young nectocatyces. 



c. Functional nectocalyces. 



d. Incipient siphons or feeding polyps, with coiled tentacle at 



base. 



e. Mature feeding polyps. 



/. Contracted branches of coiled tentacle. 



g. Palpons or sensory polypes and cystons or excretory polypes. 



h. Gonodendra. 



