134! EEVIEWS. 



therefore, not intended to be strictly accurate. Unfortunately, 

 however, this is not the only error. In his two figures of the animal 

 the proportions of the segments are different, the anterior cephalo- 

 thoracic segment being absolutely longer in the smaller figure. It 

 is, indeed, djfiicult to believe that the two drawings have been taken 

 from the same species, as the abdominal segments differ not only in 

 proportion but in number, and the length of the antennae is by no 

 means the same. Again, the abdomen, as represented in figure 5, 

 differs from that either in figures 1 or 7, agreeing, indeed, with figure 

 7 in the number of segments, but differing in their proportion as 

 well as in the form of the caudal lamellae and the number of the 

 caudal setae. Still, the drawings are good, and apparently truthful. 

 Some of the differences above alluded to (and which are by no 

 means all that might have been pointed out) may be sexual cha- 

 racters; some may be the result of mutilation; but there are 

 others which cannot be accounted for in this manner ; and as there 

 are many species of this group which are at first sight very similar 

 to one another, we suspect that in Professor Van Beneden's Plate 

 sviii., and in his description, two or more species have been eon- 

 founded together. 



The pretty little Isopod, originally described by Slabber under 

 the name of Agaat-Pissebet, has been rediscovered by Van Beneden, 

 and named by him Slabberina, after its first observer. The sperma- 

 tozoa of this species (Plate XV. figure 10) are, according to the figure 

 given, in the form of a long seta with a bundle of shorter hairs at 

 one end. If, however, we may judge from the parallel case of 

 Asellus, these bodies are not simple spermatozoa, but we have here 

 another case of bimorphism in the seminal elements. In our com- 

 mon fresh- water Asellus aquaticm, the spermatozoa are of two 

 sorts. The first are oval, or more or less elongated bodies diverging in 

 the form of a brush from a common point of attachment. Pi'om the 

 same point arise several long and slender setae, which, however, are 

 often attached together along their whole length so as to look like a 

 single filament. We presume that the same is the case with Slab- 

 berina, and that we may add this genus, therefore, to the small but 

 gradually increasing number of species in which the spermatozoa are 

 of two sorts, and which are, perhaps, destined, ere long, to throw a 

 new light on the whole subject of generation. 



An interesting chapter is devoted to the Sacculinidae. Tliey 

 are parasitic on higher Crustacea, and are the most degraded of 

 their class. The sandy shores of Ostend are inhabited by great 

 numbers of common Crabs. Three-quarters of these carry on 

 the underside of the abdomen a little yellow ball, which is sometimes 

 as large as a nut, and which, of course, prevents the abdomen from 

 fitting into its furrow. This yellow globule, at first sight like nothing 

 less than the active lively Crab, belongs nevertheless to the same 

 great group of animals, and forms the genus Sacculina of Tliompson. 

 A secoiTd member of the same family, the Peltoyaster Pacjuri, attaches 

 itself, as its name denotes, to the Hermit Crab, whose name is, indeed. 



