106 Iransadions of the 



slide, they appear homogeneous, bright, and highly refracting ; but 

 when left for a very short time a clearer longitudinal space appears 

 in the middle line at the end to wliich the rays are attached ; in 

 the centre tliis is transformed into a dark, club-shaped rod. The 

 rays are extremely fine, and in many cases scarcely perceptible ; 

 they generally have about the same length as the caput, and are 

 usually turned forward ; the only appearance of a tail is a slight 

 square projection at the narrower end ; after a short time has 

 elapsed this is superseded by a sort of effusion of extremely fine 

 sarcode resembling that of infusoria, which forms a cloud-like 

 spherical projection. After the zoosperms have been dead some 

 time, nothing remaius of them but the framework, which shows lines 

 forming an oblong, with a button-like projection internally at one 

 end. This form is represented in Fig. 4, and presents some points 

 of resemblance to the zoosperms of the common lobster. The length 

 of these bodies ranges between ■ 012 mm. and • 018 mm., and their 

 breadth is about 0' 006 mm. and 0*007 mm. The spermatophora 

 exactly resemble those I have described as belonging to P. misan- 

 thropus* to which species the present one is nearly allied. 



Porcellana jplatyclieles is a very common crab, found under 

 stones on our coast just above low- water mark at spring tides. Its 

 zoosperms differ a good deal from those of the Paguri. In the 

 typical specimens (Fig. 5 d) the caput consists of two parts, and has 

 the appearance of a rod with a knob at one end. The anterior 

 extremity of this rod is occupied by an oljlong mass of highly 

 refracting material, while the remainder of it, together with 

 the knob itself, is made up of a finely-granular nearly homo- 

 geneous sarcode, which I might have imagined to be homolo- 

 gous with the tails of the zoosperms of Pagurus, were it not that 

 the rays are derived from this part instead of from the highly 

 refracting part. They arise from the knob, and are generally four 

 in number, two on each side of a conical projection in the mid 

 line. The shape of this sarcodous part varies considerably in dif- 

 ferent specimens ; in some it becomes flat, and more or less like a 

 disk ; in others the highly refracting part is simply capped by a 

 small portion of sarcode which runs out into the rays without 

 forming any portion of the rod. In some cases the refracting part 

 is broken, a small portion being divided from the remainder and 

 lying detached in the sarcode. The total length of the caput varies 

 from O'OOG to 0* 011mm.; of this the refracting part occupies 

 • 004 mm. This part is nearly always of the same length, the dif- 

 ference in size of the zoosperms being generally caused by the sar- 

 codous material. The rays, as a general rule, equal about 3^ times 

 the length of the caput ; they become of such extreme tenuity at 

 their extremity that it is very difficult to measure them. 



* Lnc. cit. 



