118 REPORT 1860. 



He showed that the Teredo undergoes a series of metamorphoses ; the eggs being 

 developed into a sub-larval fomi after their exclusion from the ovary, and remaining 

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

 larvae) 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 " eapuchon eephalique," and 

 which is provided with two pairs of muscles of extraordinary strength.' Mr. Jeffreys 

 was of opinion that the foot of the Teredo was the sole instrument of perforation. 

 He instanced, in illustration of this theory, the cases of the common limpet, as 

 well as of many bivalve mollusks, Echinus lividus, and numerous annelids, which 

 excavate rocks to a greater or less depth ; and he cited the adage of " Gutta cavat 

 lapidem non vi sed ssepe cadendo," in opposition to the mechanical theory. The 

 Teredo bores either in the direction of the grain or across it, according to the kind of 

 wood and the nature of the species ; the Teredo Norrec/iea usually taking the former 

 course : every kind of wood is indiscriminately attacked by it. The Teredines con- 

 stitute a peaceful, though not a social community ; and they have never been known 

 to work into the tunnel of any neighbour. If they approach too near to each other, 

 and cannot find space enough in any direction to continue their operations, they en- 

 close the valves or anterior part of the 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, labouring under the idea that it 

 could no longer subsist after being thus voluntarily shut up, he considered it to be 

 the pink of chivalry and honour, in preferring to commit suicide rather than infringe 

 on its neighbour. In this enclosed state the valves often become so much altered 

 in form, as well as in the relative proportion of their different parts, as not to be 

 easily recognizable as belonging to the same species ; and one species ( T. divariccda) 

 was constituted from specimens of T. Norvegiea which had been so deformed. The 

 food of the Teredo consists of minute animalcula, which are brought within the 

 vortex of the inhalant siphon, and drawn into tire stomach. The wood which has 

 been excavated also undergoes a kind of digestion during its passage outwards 

 through the long intestine. The animal has been proved by Laurent and other 

 observers to be capable of renewing its shelly tube, and of repairing it in any part. 

 It is stated by Quatrefages (and apparently with truth ) that the sexes are separate, 

 impregnation being effected in a similar mode to that which takes place among 

 palm-trees and other dioecious plants. There appear to be only five or six males 

 in one hundred individuals. The Teredo perforates and inhabits sound wood onlv, 

 but an allied genus (Xyhphaga) has been recently found to attack the submarine 

 telegraph cable between this country and Gibraltar at a depth of from sixty to 

 seventy fathoms, and to have made its way through a thick wrapper of cordage into 

 the gutta percha which covered the wire. The penetration was fortunately dis- 

 covered in time, and was not deep enough to reach the wire. He gave several 

 instances to show the rapidity of its perforating powers,— one of them having been 

 supplied by Sir Leopold M'Clintock while he was serving with the author's brother 

 in the North Pacific. 



Mr. Jeffreys traced the geographical distribution of the Teredines, and showed 

 that at least two species, which are now found living on our own shores, occurred in 

 the post-pleistocene period ; and he inferred from the circumstance of one of these 

 species having been found in fossil drift wood, that conditions similar to the present 

 existed during that epoch. Some species inhabit fixed wood, and may be termed 

 ittoral," while others are only found in floating wood, and appear to be "pelagic." 

 Each geographical district has its own " littoral " species, and the old notion of 

 he ship-worm (which Linnaeus justly called " Calamitas Navium ") having been 



