l'().MONA (•|)I,I.K(ii; Jol KNAI, OF KNTuMuUKiV 813 



III a iiiiiiilM'r of other familit-s of spiders examined there were no hiiirs 

 of unusual types. In a few there were only a very few |)luine-like setie as in 

 the Afreleniche (Atjilmn iinrvia). where there were only a very few liairs 

 like JMtrure 255. !). 



Seta" were also stiKJiid in rxaiiiplis of more distantly related j;roups of 

 arthnipods. Figure 2M. 1(1, 11 and 12. are from a youHK Limulus. A 

 rather usual type of hair is shown in l(t. The tips of sonu' of the seta- have 

 lateral projections sueli as shown in 11. A simple type with its eomniuni- 

 cation throutih the ehitin is shown in 12. 



.\m(in}r the l'edipal|)ida. there are many hairs of the usual type such as 

 Fi^jure 2r>(), 1. hut 2 shows a rather different structure where the hair projects 

 from a little mound, and 3 shows simi)le elevations from which there are no 

 hairs ])rojeetinf;. 



Jfemhers of the I'halan^ida examined show rather usual types of hairs, 

 similar to 4 and 5. which were found on various parts of the hody of 

 Lrobunum sp. 



Atnontf the Solpujiida no new types were (>neountcred. 



The hairs of Aearina are hoth of the u.sual sort and also plume-like. 

 Herlese ('12) recently descrihed many types of plume-like hairs in various 

 species. The.se seta' were chictly from the body. 



The hairs of the jiseudoscorpions are of the usual tyjic and so far as 

 studied no other kinds are present. 



(^ominfi now to more distantly related groups we have Fijjure 2">(;, 8 and 

 9, from a lar^e dipIo|)od. The Hrst c)f these shows a hair of usual type with 

 its canal through the thick cuticle. The second of these fifiures shows a lar(?er. 

 heavier hair located on a little nuuind with the ha.se hollowed out hut the 

 cavity very slisjlit beyond this point. 



Figure 2.")(), 10-14. shows simple hairs from a chilopod. Srnlopi nilni sj). 

 Sonu- of the smallest of thi'se are just simple projections from a slipht eleva- 

 tion, one is a minute hollow elevation. Some of these simple hairs show 

 stages in their develoiiment. 



Pa.ssinir now to aiv>ther "^riiu]) of arthrojiods we find in a member of the 

 Onyehophora, Pnipnliis. very few hairs but numerous mound-like elevations 

 over the surfai'cs of the body. Sonu' of these little mounds are jrrouped to- 

 gether and from sonu^ of thest' trin- siinple seta> project : as is .shown in FiRiire 

 2.5(i. K). Some of the larirer elevations have several seta-, but most of the 

 mound-like elevations have none, and probably represent a very primitive 

 sensitive structure. 



Conclusions 



The hairs of tarantula are of two chief kinds, the usual simple sort and 

 the plume-like structure. They are of many sizes from larpe and thick to 

 short and slender. All of these hollow hairs are undoubtedly sensory, but the 

 preat variations in form and structure are probably not altogether due to 

 special sensory functions and may be more for protection. Spiders with 



