294 NOTES AND MEMORANDA. 



forms, basing this cliiefly on the presence of two pairs of stigmata, 

 and the simplicity of the male copulatory organs ; palaeontology, 

 however, aflbrcls some support to his views, inasmuch as Protolycosa 

 belongs to this group. With regard to this fossil form, Bertkau sug- 

 gests that the backwardly directed spinous processes found on the 

 right side represent the hinder pair of spinning warts, and that the 

 small spines on them are the spinning tubes. 



Researches into the Developmental History of the Spiders — 

 Tlie indefatigable Barrois has a preliminary chapter on this subject 

 in M. Robin's Journal.* The chief aim of the author was to examine 

 the arrangement of the germinal layers, and the mode of develop- 

 ment of the internal organs ; this work, which has never yet been 

 undertaken, was effected by the aid of fresh ova, and of sections 

 stained by bichromate of potash and osmic acid. Passing by some 

 remarks on the relative value of the observations of Balbiani and of 

 Ludwig, in which attention is drawn to the highly granular character 

 of the protoplasm of the formative layer, we note that Barrois 

 adds something to the observations made by Claparede on the primitive 

 streak ; the latter admirable student had noted the appearance of 

 thoracic, abdominal, and post-abdominal zonites, but he did not note the 

 presence of two cords, formed of several rows of embryonic cells ; to 

 these Barrois gives the name of germinal hands ; they are derived from 

 a primitively continuous mesodermal layer, and are found throughout 

 the whole length of the body, although they are largest in the thoracic 

 region ; in this they may be seen to be dividing into a median 

 (nervous) and a peripheral portion ; more anteriorly, they form the 

 cerebral lobes (procephalic lobes of Claparede and Huxley) ; on the 

 whole this region is, at this period, strikingly like the same parts in 

 the Scorpions, the development of which have been already described 

 by Metschnikoff. Behind the thoracic region there are ordinarily ten 

 zonites, of which the first four are provided with the rudiments of 

 appendages. 



By following out the stages of development step by step, Barrois 

 has been enabled to discover a stage — to which he applies the term 

 Limuloid — which was not observed by Claparede. In this state the 

 embryo has an exceedingly remarkable appearance ; it is divided into 

 two distinct parts, thoracic and abdominal ; the posterior portion is 

 formed by the fusion of all the tergal arcs, in which, however, it is 

 possible to observe a jire-abdomen, consisting of six, and a post-abdo- 

 men, consisting of four segments. Of the former series four are 

 larger than the other two, and are seen to be provided with appendages ; 

 the anal segment, if examined from its ventral surface, is found to be 

 made up of three segments, so that there are altogetlier twelve seg- 

 ments in the abdomen, or six in the post-abdomen, and the number of 

 these in the Spiders is found to correspond with those of the same 

 region in the Scorpions. In one of the Xiphosura, Hemiaspis limu- 

 loidcs, the arrangement of parts is strikingly similar to what is here 

 observed in the embryo of the Spider ; the higher development of 



* ' Journ. Anat. Thys.,' xiv. (1878) 527. 



