ON INDO-MALAYAN BARNACLES. 7<5 



developing into animals of the ordinary shape with a capitulum and a peduncle, did 

 not acquire the size of the older specimens, and lost their female genital apparatus " 

 {Challenger Reports, Vol. X, Cirripedia (2), p. 21). 



In 6". squamuliferum, in which the complemental males can only be found occasion- 

 ally, young hermaphrodites and complemental males occur together on the edge of the 

 opening and are difficult to distinguish from one another by the naked eye, the males having 

 a well developed peduncle in spite of their minute size. Inbreeding specimens of S. sociabile 

 no males were found ; but the same thing has occurred with respect to several assemblages 

 of S. squamuliferum, which were just as rich in individuals and some of the individuals of 

 which were breeding. Possibly cross-fertilization is necessary or beneficial from time to time, 

 but not invariably, just as fertilization only occurs at all either periodically or under cer- 

 tain conditions in many of the lower Crustacea. Even in those species of Scalpellum in 

 which complemental males are believed to be always absent (e.g., 5. balanoides, Hcek), 

 it is quite probable that this may be the case, for very little can be known of the bio- 

 nomics of the fauna of the oceanic abysses even under the most favourable conditions. A 

 solitary specimen, or half a dozen specimens, in the way of which the dredge has chanced 

 to come, may be the sole representative or representatives, as far as zoologists are con- 

 cerned, of a species extremely common in its own place. Moreover, the few examples of 

 such species in our museums can only be examined dead, and (even though the minute 

 structures of the internal organs of specimens from great depths are often in an extra- 

 ordinarily good state of preservation, whatever may have happened to their integument), 

 it is by no means safe to argue similarity of function from similarity of structure in all 

 cases. 



Several of the individuals in the two assemblages of 6*. sociabile bear eggs. These are 

 arranged in large, fan-shaped lamellse on each side of the body. Each lamella is one 

 layer deep but contains a considerable number (over 50) of ova. It is attached at its 

 base to a well-defined club-shaped process of the sack or mantle. The eggs are minute, 

 nearly globular, but with one axis very slightly longer than the other two, of a pale yellow 

 colour. All of them, in different individuals, seem to have reached approximately the 

 same stage of development, which is one of segmentation. 



In connection with the formation of the assemblages it would be interesting to know 

 how long the life of an individual lasts. There are many minute individuals among the 

 specimens, but it seems improbable that a whole year should have elapsed between the 

 birth of such small ones and the production of the eggs which were commencing to develop 

 when the specimens were taken. It is known that some Barnacles 1 grow with great rapi- 

 dity (see Darwin, op. cit., p. 63). I have seen many flourishing assemblages of Lepas 

 fascicularis attached to floating feathers off the coast of Iceland (Westman Straits), and it 

 is obvious that such species as Dichelaspis equina and D. pellucida must perish whenever 

 their host, be it crab or sea-snake, casts its skin. The enormous swarms of such Crus- 

 tacea as Calanus finmarchicus in the seas of north-western Europe show that a high 



I I have lately obtained a specimen of Balanus tintinnabuluni (Linn.) from a buoy in the Pamben Channel which had only 

 been in the water for about twelve months. The shell measures 65 mm. by 60 mm. Sept. 35th, 1905. 



