424 



CRUSTACEA ENTOMOSTRACA. 



Lithotrya Sow., with an elongated peduncle covered with scales, and 

 eight plates on the capitulum ; the body is sunk in the cavity of the 

 peduncle ; the animal lives in deep burrows which it excavates in cal- 

 careous rocks, corals or shells ; tropical, hermaphrodite. Ibla Leach, 

 attached to littoral objects in the warm seas of the eastern hemisphere. 

 /. Cumingii Darw. Contrary to the general rule among cirripedes 

 the sexes are separate and exhibit marked dimorphism. In the female 

 the scuta and terga only are developed and they are not calcareous 

 but horny. The peduncle is covered with spines, and the body is partly 

 sunk within its cavity. The first pair of cirri is separated by a consider- 

 able interval from the remainder. The males are minute degenerate 

 creatures, and one or more are attached within the mantle cavity of the 

 female. The capitulum is almost undeveloped, but the peduncle is 

 comparatively large and tapers to a point, which is embedded in the 

 tissues of the female and bears the characteristic prehensile antennae. 

 The mouth parts are well developed and a complete alimentary canal is 

 present, but the thoracic appendages are reduced to two pairs, apparently 

 the 5th and 6th, and these are small and irregular. There are well de- 

 veloped testes and vesiculae seminales but no penis. Philippines and 

 Burmah, attached in groups to the peduncles of Pollicipes mitella. The 

 other species, /. quadrivalvis (Cuv.), from the Australian seas, consists of 

 hermaphrodite forms and " complemental males." The hermaphrodite 

 forms resemble the female of I. cumingii except that, like most Cirripedes, 

 they possess the male reproductive organs in addition to the female. The 

 males also resemble those of the other species except that there are a 

 distinct penis and a caudal fork the halves of which are divided into three 

 segments. The caudal appendages of the hermaphrodite form are remark- 

 ably long. Scalpelhim Leach, presents similar remarkable instances of 

 sexual relations. In the hermaphrodite or female form there are 12-15 

 calcareous plates on the capitulum and the peduncle is nearly always 

 squamiferous. In all the living species that were known when Darwin 

 wrote his monograph, small male forms are attached to the number of two 

 or more about the body of the other form. In some cases these are dis- 

 tinctly pedunculated, the capitulum carries calcareous plates, and an 

 alimentary canal and 6 pairs of cirri are present. In S. ornatum and S. vul- 

 gar e however the males are reduced to flask-shaped bodies, without an 

 alimentary canal, with 4 minute calcareous plates, and only four pairs 

 of cirri which are nonprehensile. In others again the valves have 

 completely disappeared. They always however retain the characteristic 

 cirripede antennae, by which they are attached. The more degenerate 

 males are contained in small pocket-like cavities on the inner surfaces 

 of the scuta of the other form, they are without a functional alimentary 

 canal and it is probable that many of these short-lived forms successively 

 occupy the scutal pouches. In S. ornatum the larger form is, according 

 to Darwin, female, and this may be the case in one other species, but in 

 S. vulgare, rostratum, peronii and villosum the larger form is herma- 

 phrodite, although, possibly in relation to the presence of the com- 

 plemental males, the male system of the hermaphrodite form is in 

 some cases under -developed. The species are found attached to the 

 slender branches of hydrozoan colonies. S. vulgare, British and adjacent 

 coasts. Many species are found in the deep sea (over 2,000 fms.). Among 

 41 new species ofScalpellum in the " Challenger " collections (about half 

 of them represented by a single specimen), Hoek found the reduced 



