ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 335 



shut during tlie day-time if tlie weather seems to threaten a heavy 

 rain-storm. 



The ants, though provided with very formidable stings, are 

 exceedingly mild and unwarlike. They present the same habits of 

 "harvesting" as those which were previously known to occur in 

 allied species of Florida and Texas. 



y. Arachnida. 



Pycnogonida.* — After a review of what has been done by pre- 

 ceding naturalists, Dr. P. P. C. Hoek discusses the general form of 

 the body ; this is strictly bi-lateral, with a proboscis, four segments, 

 and a rudimentary abdomen. The first segment is formed of one 

 cephalic and of one thoracic ring ; the proboscis ought not to be 

 regarded as a head, it varies in form, and in length, and in the mode 

 of its attachment to the cephalothoracic segments. The body may be 

 slender or robust, the segmentation distinct or obscured ; the abdomen 

 is represented by a single joint, the length of which varies consider- 

 ably ; the surface of the body may be smooth or hairy, with or without 

 tubercles or spines. There are never more than seven pairs of 

 appendages, and when all are present three belong to the cephalo- 

 thorax, and are known respectively as mandibles, palpi, and ovigerous 

 legs ; when the first are complete, they have three joints and a 

 terminal pincer (Pallenopsis) ; in some cases (Pycnogonurn) the 

 mandibles altogether disappear in the adult state. The palps would 

 appear to have primitively a number of joints, and this number varies 

 even within the limits of a genus. There may be ten joints or as 

 few as three, or the palps may disappear altogether. The females of 

 all species, however, retain the ovigerous legs, and they are frequently 

 also represented in the male. The nervous system consists, as usual, 

 of a cerebrum, an oesophageal collar, and a ventral ganglionic chain ; 

 in the last there are four or five ganglia, Phoxichilus presenting an 

 intermediate condition in having the first of its ventral ganglia small 

 in size, and closely applied to the second ; all are distinctly bilobate, 

 the coalescence of the paired parts being complete. Concrescence 

 never attains to the extent exhibited in the Brachyurous Crustacea, 

 for even in AmmoetJiea it is possible, by the aid of reagents, to discover 

 the connecting fibres. Nor, indeed, can external form be taken as 

 giving any true idea of the extent of fusion, for Pi/cnogonum, in 

 which there is an extreme condition of external " concentration," has 

 the ganglia separated by some considerable distance. After a further 

 discussion of allied points, the author states the eyes of the Pycno- 

 gonida have generally a very complex composition ; ganglion-cells 

 and rods can always be made out, but there would not appear to be 

 any vitreous body ; a lens is developed from the integument. The 

 buccal orifice is triangular, and almost immediately dilates into a very 

 large pharynx ; at its end there is a constriction and a canal is 

 developed, the length of which depends on that of the cephalic part 

 of the cephalothoracic segment. The inner face of the cells lining 



* Arch. Zool. Expe'r. et Gen., ix. (1881) pp. 445-542 (8 pis.). 



