CIRRIPEDIA. 



431 



At the stage at which this remarkable Cirripede can next be recognized 

 it has taken up its position in the connective tissue of its host between 

 the intestine and the muscles lying in the ventral wall of the abdomen.* 

 The internal Sacculina, as it is now called, consists of a rounded mass of 

 cells, containing a minute compact body, the primitive ova, and con- 

 tinued at its edges into long root-like processes which ramify throughout 



R. 



FIG. 278. Longitudinal sections through two stages of development of Sacculina carcini 

 (from Korschelt and Heider after Delage). A Sacculina interna ; B Sacculina externa ; a 

 atrium (widening of the oviduct) ; am outer'mantle layer ; b brood-cavity (mantle cavity) ; 

 B basal membrane ; C central tumour ; cl cloacal opening ; D intestinal wall of host ; dr 

 cement glands of the ovarian sac ; / aperture of the perivisceral cavity ; g ganglion ; im inner 

 mantle layer ; L body-wall of host ; ov ovary ; p psrivisceral cavity ; pe perivisceral 

 ectodermal layer ; R root processes (some in cross section) ; t rudiment of testes. 



the soft tissues of the host, even to the tips of the extremities. The crab's 

 heart and branchiae alone are free from the ramifications of its parasite 

 (Fig. 277). As the central mass slowly grows, it begins in time to press 

 against the ventral wall of the abdomen of the crab, which softens and 



* Mr. G. Smith has recently recognized the parasite when it formed a 

 mass not more than 2 mm. in diameter, and lay considerably in front 

 of its final position. 



