174 



PORIFERA. II. 



genus, with the only exception of the above mentioned Pocillon l ). The chela is a palmate anisochela, 

 whose smaller end is considerably smaller than the larger one; from the axial recurving of the smaller 

 end a sharp spine or spur issues. The chelae may in some species occur in two different sizes. In a 

 few species they may also form rosettes, and then, as is generally the case, only the large chelae form 

 rosettes, while the small ones, when such are found, are never gathered in rosettes. Neither are 

 bipocilla known outside the genera Iophon and Pocillon 2 ). The author who first mentions these bodies 

 is Bowerbauk; his description of them, like his descriptions of the chelae upon the whole, is defi- 

 cient, and he calls them in different places and according to the different positions in which he finds 

 them < uuipocillated and < bipocillated bihamates:> or <bipoeillated anchorates*. Gray calls them 

 «bipolicated anchorates>, I suppose on account of a misreading of Bowerbank. Vosmaer (Niederl. 

 Arch, fiir Zoologie, Suppl. Band I, 1881, 82) says that they are probably a modification of sigmata. 

 Ridley and Dendy calls them < bipocillate spicules* or «bipocilli» 3), and of the peculiar bipocillum 

 in Iophon chelifer they say that they are inclined to regard it as a much modified anisochela. Top- 

 sent says also in 1901 (Resultats du Voyage du S. Y. Belgica, Spongiaires), under Iophon radiahts that 

 the bipocilla must be regarded as modified anisochelse, but his reason for this opinion, that their 

 smaller end shows a fine dentation, is scarcely of any importance. Thiele, finally, in 1903 (Arch, fiir 

 Naturgesch. 1903, I, 389) calls the bipocilla anisochelse without any further explanation. — The common 

 form of the bipocilla had never been correctly described till the appearance of Wilson's work, mentioned 

 below. Generally, as by Ridley and Dendy, they are described as consisting of a shaft with a cup-like 

 expansion at each end. Wilson in 1904 (Mem. of the Mus. of comparative Zoology at Harvard College, 

 XXX, Nr. 1, 143 — 154, PI. 19, fig. 6 b— e, PI. 20, fig. 6 a et c, fig. 15 a, c— f) gives for the first time a thorough 

 description of the construction of the bipocilla in the species treated by him; here for the first time a 

 correct and exact description is given, together with good figures. The author does not say that the bi- 

 pocilla are to be regarded as chelae, but he calls the peculiar bipocilla in I. chelifer and lame Hat a .chelate 

 bipocillus ■<>. — The bipocilla are in reality somewhat modified anisochelse, and the principal modification 

 is that a tooth only is developed in one end, which may be designated as the upper end. The bipo- 

 cillum, in its common and typical form, consists of a curved shaft, which has always an exceedingly 

 fine brim on either side. At the lower end the shaft is so much recurved, as to form about a right 

 angle with the middle part of the shaft, but the curve is round and even; in this recurved part the 

 lateral brim of the shaft is broader, and therefore this part has a somewhat spoon-like form. At the 

 upper end the lateral brim is also a little widened and forms a pair of small alse; then follows, as 

 usually, a thin connection with the tooth, formed by the shaft alone; the tooth is a comparatively 



■) Carter (Ann. Mag. Nat. Hist., Ser. 5, IX. 291, PI. XI, fig. 16 e, f) mentions and figures a very small chela occurring 

 in his Esperia /cevis, which might seem to be of the fop/ion-type, as Carter also remarks. Esperia l&vis is evidently a 

 Mycale, and it has a typical il/yctf/e-anisocheia ; how the fact really is with regard to the small chela, whether it is an extra- 

 neous fop/ton-che\a. or a peculiar chela belonging to the species, cannot be decided. 



2 ) In a work by Swartschewsky (Beitrag zur Kenntniss der Schwamm-Fauna des Schwarz. Meer. , Kiew Natur- 

 forsch. Gesellsch. Schrift. XX, 27, 51, Taf. 5, Fig. 5 a— d) published in 1905, the author establishes a species EspereUa Iophon; 

 it seems to be a Mycale, and it has typical A/yra/^-anisochelse gathered in rosettes, but besides it has smaller chela, which 

 may be more or less, and often highly, curved; in the latter case, the author says, they assume the form peculiar to the 

 bipocilla. To judge from the figures, some of these chelae may seem to be bipocilla, but perhaps the question is only of 

 peculiarly formed anisochela, and they seem also by transitions to be connected with the common chela;. 



3) As pocillum is a neuter noun, I use the plural form bipocilla. 



