SCIENCE-GOSSIP. 



283 



often obscure or forgotten names, the work will 

 never stop if it is going on at its present rate ; a 

 little injustice of this kind may be easily passed 

 over. I see our British Helices are now divided 

 into fourteen or fifteen sub-genera. Cannot some 

 enthusiast for this sort of thing make a few 

 more ? — Alfred Bell, London. 



Parasite of Tortoise. — I can supplement to a 

 small extent Mr. Howarth's very interesting note 

 in last month's Scien"CE-Gos.sip (ante p. 236) 

 respecting his discovery. A tortoise was bought 

 from a man in the street in the spring of 1895 ; 

 it was placed in the garden, and soon afterwards I 

 discovered on it, in various places, a number of the 

 parasites. There were four in good condition and 

 the incomplete remains of several others. On 

 attempting to remove them they were found to 

 be so firmly attached that it was impossible with- 

 out risk of damage. The tortoise did not appear 

 inconvenienced when even strong traction was 

 made, except in the case of one, which was fixed 

 in the somewhat thinner skin lying between the 

 front legs and neck. When this one was touched 

 the tortoise withdrew itself sharply, as though 

 pained. I believe from general appearances that 

 this was the only living specimen. Both paraffin 

 and sweet oil were applied in hopes of killing the 

 creatures, if not already dead, and obtaining them 

 without injury, but they held on just the same 

 after the application. Finally one was removed 

 by main force, plus a piece of the host's skin, 

 another came off entire, with the mouth organs 

 complete, the other two left them imbedded, but 

 one set was extracted without injury afterwards. 

 On examination under the microscope, my speci- 

 mens agree so closely with Mr. Howarth's drawings 

 that there can be no doubt as to the identity of the 

 species, although none of them have been so fortu- 

 nate as to show the lancets extruded. The antennae 

 exactly correspond, and the curious tufts of hairs at 

 the apex, shown at fig. b, are especially noteworthy. 

 Eyes are absent. In all my specimens the two 

 halves of the double proboscis, however, lie closely 

 together, and on the under side there is a structure 

 not in the drawings. It is a kind of case, or partial 

 sheath, very like the under half of a duck's bill in 

 shape, somewhat concave on the upper side, and in 

 this hollow the pair of tubes lie, partly enclosed 

 and protected by it, and it extends a little beyond 

 their ends. At the tip, and for about one-half of 

 the length behind it, there is a number of triangular 

 tooth-like projections pointing backwards, and it is 

 these projections which give the owner such a 

 secure hold on the skin of its unwilling host. It is 

 easy, on looking at them, to understand how, even 

 in death, the attachment would still be main- 

 tained, and that nothing probably but destructive 

 force would effect removal. A similar structure 

 does not exist on the upper side, unless, indeed, 

 in all my specimens it has become detached 

 and lost, as was e\-idently the case with the 

 lower side in the one from which the drawings were 

 made ; but there is no evidence of rupture visible 

 in mine. From its position and structure it may 

 be concluded that this sheath is the weapon which 

 first punctures the tough skin of the tortoise and 

 enables the somewhat delicate tubes with their 

 enclosed lancets to enter without injury. The legs 

 appear to be weak and ineflicient, the tarsi especially 

 so, and probably the animal — particularly the 

 female — having once obtained a suitable position 

 on the host seldom or never quits it. In fig. d a 

 kind of pad may be seen under the terminal claws. 



which is, I think, referred to in the appended family 

 description and would be useful in crawling over 

 the slippery, hard skin, where claws alone might 

 fail. There is but very scanty notice of this 

 parasite in any books accessible to me. In the 

 Rev. J. G. Wood's " Natural History," 1863 edition, 

 page 683, the following occurs : ' ' There is hardly any 

 animal which is not subject to the attacks of these 

 tiresome mites, and even the hard-shelled tortoise 

 itself is not free from them. They fix themselves 

 so firmly with their barbed grapnels that if they 

 are roughly torn from their hold they either leave 

 their heads in the wound or carry away part of 

 the flesh." In the table of generic distinctions, 

 page 801, the family Ixodidac- is described : " Body 

 with leathery covering; beak blunt, toothed at tip, 

 barbed at middle ; last joint of feet two-clawed, 

 with vesicle." Genus Ixodes described same as 

 family ; no doubt our specimens belong here. In 

 Carpenter's " Microscope and its Revelations," 

 seventh edition, there is a good deal of information 

 about the family scattered through page 932 and 

 several following. — Jas. Burton, 9, Agamemnon Road, 

 West Hampstead. 



Charles Darwin and Heredity. — Professor 

 Poulton, of Oxford, in a recent work on Charles 

 Darwin, remarks as follows : " Darwin's power was 

 largely due to the inheritance of the imagination of 

 his grandfather, combined with the acute observa- 

 tion of his father. Although he possessed an 

 even larger share of both these qualities than his 

 predecessors, it is probable that he owed more to 

 their co-operation than to the high degree of their 

 development." Now, some people who carefuU}- 

 consider this passage will not agree with the 

 learned Oxford Professor. Powers of imagination 

 and of acute observation do not co-exist in the 

 scientific intelligence, and the late Charles Darwin 

 was not very strong in the latter attribute. The 

 grand secret of his success was his singular power 

 of literary imagination, which the force of circum- 

 stances, habits, character, etc., directed into a 

 particular field of thought. His grandfather had 

 fought very valiantly in the endeavour to manu- 

 facture poetry out of bald and dry scientific 

 material. The illustrious grandson attempted 

 precisely the same feat ; but his plans and course 

 of procedure were decidedly more astute and more 

 carefully prepared. Modern scientific investigators 

 commence work by anah-sing the concrete so as 

 to arrive at a general fact or law. In doing so 

 they develop any amount of experimental subtlety ; 

 but if anything apparently anomalous or excep- 

 tional is encountered they laj' it aside and await 

 further information about it. Not so Darwin. 

 He failed to find the facts bj' analysis, but he 

 eagerly grasped the exceptions, however trifling 

 or insignificant, and it was these that set his 

 imagination agoing. For instance, he noticed in 

 the course of experiments directed to another 

 object that the offspring of a cross were superior 

 in vigour to seedlings of self-fertilized parentage ; 

 and it has been said that the whole of the 

 important researches into the effects of cross- and 

 self-fertilization originated in this accidental 

 observation. As a matter of fact, as is now 

 well-known, this superiority in \-igour is merely 

 exceptional, and self-fertilizers are immensel}- more 

 productive than those dependent on insect aid. 

 However, the observation was eagerly seized as 

 an appropriate pabulum for Darwin's inimitable 

 theorizing faculties. — Dr. P. Q. Keegan, Patterdale, 

 Westmoreland ; January, 1S97. 



