224 YEAR-BOOK OF FACTS. 



that it was curious to find this creature possessing the rudiments of 

 eyes, for, in all other cases where creatures lived in the dark, they 

 Lad no eyes at all. Mr. M 'Andrew stated that he had described a 

 species of Crustacea, dredged from a very great depth, that did not 

 possess eyes. 



TEREDINES, OR SHIP-WORMS. 



Mr. Jeffreys has read to the British Association a paper on 

 Teredines. He treated the matter first in a zoological point of view, 

 and gave a short history of the genus Teredo, from the time of 

 Aristotle and his pupil Theophrastus to the present time, especially 

 noticing the elaborate monograph of Sellius, in 1703, on the Dutch 

 Ship-worm ; the valuable paper of Sir Everard Home and his pupil, 

 .Sir Benjamin Brodie, in 1S06; and the physiological essays of 

 Quatrefages, in 1S4D. He showed that the Teredo undergoes a series 

 of metamorphoses ; the eggs being developed in a sub-larval form 

 after their exclusion from the ovary, and remaining hi the mouth of 

 the parent for some time. In its second phase (or that of proper 

 larva;), the fry are furnished with a pair of close-fitting oval valves, 

 resembling those of a Cythere, as well as with cilia, a large foot, and 

 distinct eyes, by means of which it swims freely and with great 

 rapidity, or creeps, and afterwards selects its fixed habitation. The 

 larval state continues for upwards of 100 hours, and during that 

 period the fry are capable of traversing long distances, and thus 

 becoming spread over comparatively wide areas. The metamorphosis 

 is not, however (as Quatrefages asserts), complete ; because the 

 young shell, when fully developed, retains the larval valves. 



He then discussed the different theories, as to the method by which 

 the Teredo perforates wood, giving a preference to that of .Sellius and 

 Quatrefages, which may be termed the theory of " suction,' - aided by 

 a constant maceration of the wood by water, which is introduced into 

 the tube by the siphons. This process, according to Quatrefages, 

 is effected by an organ which he calls the " capuehon ciphaliqut," 

 and which is provided with two pair of muscles of extraordinary 

 h. .Mr. Jeffreys instanced, in illustration of his theory, the 

 of tin' common limpet, as well as of many bivalve molluscs, 

 Echinus UvidtU, and numerous annelids, which excavate rocks to a 

 greater or Less depth ; and he cited the adage of " Gutta cavat 

 Lapidem non vi Bed bsbm oadendo," in opposition to the mechanical 

 theory. The Teredo bores either in the direction of the grain or 

 it, according to the kind ofwood Mid the nature of the species ; 

 il..- Teredo Norvaffica usually taking the former course: every kind 

 of wood is indiscriminately attacked by it. The Teredines constitute 

 a peaoefol, though nut a social community ; and they have 

 been known to work int.. the tunnel of any neighbour. If they 

 approach too near to each other, ami cannot find space enough in any 

 direction to continue their operations, they inclose the valves or 

 anterior part of tin- body in a case, consisting of one or more hemi< 

 spherical layers of shelly matter. Sellius supposed that the Teredo 



ate up the wood which it excavated, and had no other food ; and, 



