SPIDER GOSSIP. 25 



from one side to the other. A cross section, although otherwise 

 not showing the gills so well, would show this, because we should 

 then see the sides of the leaflets, whereas in the figure given we 

 see the ends (at "opening for air"), where leaflet is joined to 

 leaflet. But it does not matter much which way you regard the 

 organ. The blood-cells are nearly as large as those of human 

 blood, the disc h. b. c, in Fig. 3, giving the comparative size of a 

 human blood-cell. 



I must now briefly describe the brain and nervous system, and 

 then close this paper. A spider has a distinct brain — which an 

 insect has not : />., all the various functions are controlled by a 

 central ganglion, or nerve-junction, instead of by smaller ganglia 

 distributed along the body and forming a " ventral cord," as is the 

 case in insects. This brain is in the lower part of its head- 

 thorax, in its chest, so to say, and contains both nerve fibres and 

 nerve cells (Fig. i, b?-., and Figs. 5 and 6). It is made up of 

 smaller ganglia, denoted by the protuberances in the figure. The 

 optic ganglion is shown giving off two optic nerves to the two eyes 

 which come into the section. A spider has eight eyes altogether. 

 Each pair of legs and jaws is controlled by its own ganglion, and 

 in the figure the abdominal ganglion is seen giving off a good 

 thick bundle of nerves. This disappears just as it gets into the 

 abdomen, because I cannot trace it any further, but of course the 

 nerves really go to each separate organ. By the brain we are 

 brought as close as may be to the seat of a spider's will, just as, 

 when we looked at the blood, we saw its seat of life. We cannot 

 " explain " these by calling them " functions of the brain," etc. — 

 that is only the same statement in other words. Truly, in the 

 humble spider there is very much to wonder at and admire. 



EXPLANATION OF PLATE III. 



Lengthwise section of Garden Spider, Epeira diadema, female, 

 showing internal anatomy:—^)/., eyes; p.p., poison-glands; lit, 

 heart; in., intestine, alimentary canal; I., liver; r. , rectum; 

 d.t., d.t., sp., discharge-tubes on spinnerets; o. , slit or opening for 

 air (see Fig. 2); op., ovipositor; p/i. , pharynx (see Fig. 5); br., 

 brain (see Figs. 5 and 6) ; thr. , throat (see Fig. 0) ; und. , under-lip ; 

 m., mouth ; /., fang ; j., jaw. Magnified 20 diameters. 

 Journal of Microscopy and Natural Science. 



New Series. Vol. II. i88q. d 



