50 



HAllDWICKE'S SCIENCE-GOSSIP. 



[March 1, 1869. 



' ocellus," a mere pigment speck behind the base of 

 each of his fifteen-jointed antenna?, and he has the 

 smallest possible tlireadlet of an optic nerve. I ex- 

 pect he cannot see, in the ordinary sense, but can dis- 

 tinguish between the light with which he has nothing 

 to do, and the darkness in which he feels his way 

 about with his antennae when doing his duty like a 

 humble vegetarian jackal, or adjutant. 



The Myriapods have been placed at different 

 times in different classes of the animal kingdom : 

 in one famous system we find them under the head 

 of Crustacea ; another, in remote times, ranged them 

 with the Hemiptera and Orthoptera as "insects 

 which only undergo a partial metamorphosis. 5 ' 

 They have slight affinities with both, and even with 

 the Annelids ; like the latter, they grow in length 

 by the successive addition of new segments between 

 the penultimate and anal. The lower subdivision, 

 the Chilognatha, by the situation of their repro- 

 ductive orifices, seem to betray Crustacean relation- 

 ships ; but we remember that in the first phase of 

 their development they displayed three pairs of legs 

 only, like the typical hexapod insect. They appear 

 to stand out the strong, well-marked, first link of 

 that long chain which bridges over the mighty gulf 

 which rolls between the creeping worm and the 

 flying insect. The Myriapod is the lowest articulate 

 animal, the Annelid the highest annulose — i. e., 

 according to the old scheme of classification, the 

 latter term has recently been used with a widely 

 extended signification. Ten years ago the sub- 

 division Ckilopoda consisted of four families, 

 including ninety-four genera ; and the lower sub- 

 division, Chilognatha, of four families, containing 

 seventy-five genera; a tremendous total of variations 

 of a type ; but since then they have been shuffled 

 and cut, and lumped and split, like the German 

 States, till nobody knows which is which. 



" An articulation complete in all its mechanical 

 appliances is not produced in the animal kingdom 

 below the Myriapod. A joint is the symbol of 

 organic superiority ; it is not an arbitrary symbol ; 

 it is a unit in an assemblage of signs which proclaim 

 a newer and higher combination in the arrangements 

 which constitute 'life. 5 At this limit in the animal 

 series the fluids and the solids of the organism 

 undergo a signal exaltation of standard. The system 

 of the chylaqueous fluid exists no longer in the adult 

 organism, it is present only in the embryonic. It is 

 supplanted by that of the blood proper. Coinciden- 

 tally with the 'joint' at the frontier of the 

 articulate sub-kingdom there occurs a heart to 

 circulate the blood, fibrine, and with it an order of 

 floating corpuscles more highly organized in the 

 fluids ; a wondrous development of the muscular 

 apparatus, stria; in the muscle-cell, a rapid increase 

 in the dimensions of the cephalic gangliaj and in 

 those of the organs of the special senses. It is here 

 in the history of the reproductive system that the 



dioecious character is first unquestionably assumed. 

 These are noteworthy events in the ascensive march 

 of organic architecture." — Dr. Williams, Mag. Nat. 

 Hist., 1854. 



The armour-plates of the cylindrical lulus are 

 composed of a semi-crustaceous hard substance, but 

 in the Scolopendridce, which our " false wireworm " 

 closely approaches, the integuments are of a flexible 

 chitinous substance, the back of each segment is 

 covered by a plate, the ventral surface by a some- 

 what smaller plate, the epimeral portions, as well as 

 the interspaces between the somites, are covered by 

 a loosely fitting coriaceous membrane of much 

 thinner texture. 



The circulating system has been a battleground 

 for men with great reputations. The nervous and 

 reproductive systems, and the development day by 

 day from the ovum, have been drawn out with 

 elaborate minuteness by Newport — in Philosophical 

 Transactions for 1841 and 1843— but I have not yet 

 fallen in with a drawing of their tracheary system, 

 which is well worthy of careful study. 



The spiracular orifices are not placed as in insects 

 between the segments, but in the side of each, a 

 little below the dorsal plate ; they are not minute 

 apertures, nor vertical slits, neither are they 

 furnished with " guards " of setse, or hairs, to 

 exclude dust aud foreign bodies ; but they are 

 circular openings, each with a well-defined hard- 

 looking ring, over which the tough but pliable 

 lateral membrane passes, lining the entrance, which 

 is directed slightly backwards, and can be closed by 

 a sphincter muscle. The tracheae are very large in 

 the anterior segments, occupying no small portion 

 of their internal cavities, but they decrease in 

 diameter in proportion as the segments recede from 

 the head ; possibly there may be ueed for a more 

 abundant supply of oxygen in the region of the brain, 

 and in the first formed portions of the body, than in 

 the equally large but more remote additions which 

 are from time to time developed near the caudal 

 extremity. 



Let us detach half a dozen pairs of spiracles, with 

 their tracheal appurtenances complete, from the 

 dissected tail end of Geophilus the much maligned, 

 float them on to a slide, and bring the " two-thirds 

 objective " to bear upon them. (Fig. 41.) 



A ladder of shining silver, a very Jacob's ladder, 

 bright and beautiful enough to have been let down 

 from heaven for the feet of angels. 



The six uprights aud the cross rungs are all 

 constructed of the same tubular wire rope 

 glistening with a dazzling metallic lustre, and 

 without a flaw anywhere. The tubes are composed 

 of an outer and an inner coat, containing between 

 them the spiral coil, to which they are closely 

 attached ; a delicate membrane also connects the 

 turns of the spiral with each other. It is interesting 

 to compare these animal breathing tubes, with their 



