10 Coelenterata. 



beneath the bases of the tentacles. //. farinacca, Verr. has a similar sphincter. 

 See also Wyragewitch. 



Carlgren( 2 ) describes the methods adopted in the Actiniaria for the pro- 

 tection of the young. In many cases the coelenteron (either its central 

 part or its lateral chambers) acts as a brood pouch. In temperate regions 

 the embryos seldom remain within the mother after the formation of 12 ten- 

 tacles, but in Urticina and Actinostola from the Arctic the young reach a 

 considerable size before they are discharged. In a specimen of A. spifaber- 

 gensis the author found a young individual with 48 tentacles, and in U. crassi- 

 cornis nearly all the Q contained embryos in the coslenteron among which 

 young specimens with more than 24 tentacles were not uncommon (one indi- 

 vidual with 76 tentacles was contained in another with 80 tentacles). Special 

 brood pouches in which the young undergo their development are also found 

 in Actiniaria [see Bericht f. 1893 Orel, p 11 Carlgren( 2 )]. In Epiactis marsu- 

 pialis n. on the proximal half of the body wall there are longitudinal rows 

 of small sacs, formed by invagination of the body wall, which project into 

 the coelenteron and lie principally in the exoccels. Each contains an embryo 

 whose pedal disc is usually close to the opening of the sac; some of the 

 embryos have 12 tentacles and 6-12 pairs of mesenteries. The author has 

 described in Condylactis georyiana from South Georgia brood pouches occurring 

 over the whole area of the body wall. There are 1-3 young in each pouch, 

 some in the gastrula stage and others with 12 tentacles and 12 pairs of 

 mesenteries. He believes that the cases described by Verrill (1899) in Epi- 

 yonactis fecunda and regularis are similar to these brood sacs. In Marswpif&r 

 Valdiviae n. from Kerguelen there are 6 large sacs which open by apertures 

 and do not communicate with the coelenteron. The central part of each brood 

 sac lies in the endocoel of a pair of secondary mesenteries, the lateral parts 

 extend into the two neighbouring exocojls. Another pouch, more expanded 

 than this, extends still further into a primary endocoel. The largest of them 

 contains more than 100 embryos, several of which have 8 fully developed 

 Edwardsia-mesenteries and 4 undeveloped ones. The brood-bearing Arctic 

 and Antarctic Actiniae do not belong to the same families, the former being 

 Tealidse, the latter Actiniidse or Paractidse. The author, in discussing the 

 means by which the embryos come to lie in the brood pouches believes that 

 the young ciliated embryos leave the coelenteron of the mother and seeking 

 the outer body wall become attached there. By stimulating the region around 

 their attachment they induce the formation of the depression in which they 

 are found in Epiactis prolifera, and on this may also depend even the origin, 

 from similar primitive sacs, of the brood pouches of E. marsupialis , Condy- 

 lactis and Epigonactis. At least in E. marsupialis the embryo itself causes 

 the formation of the brood sacs, as in another well preserved female no pouches 

 are present. On the contrary in Marsupifer the brood sacs are already formed 

 before the entrance of the embryos. 



Immermann describes the relation of the young stages to the adults in 

 5 specimens of Epiactis prolifera Verr. Young individuals of quite different 

 sizes are found attached to the sides of the body just above the pedal disc, 

 but without any regular order. The position from which a young spe- 

 cimen has been removed is indicated by a flat depressed area surrounded by 

 a raised border formed by the ectoderm of the adult. The bottom of this de- 

 pression shows impressions of the septa of the young animal, but there is no 

 communication between the adult and the young anemone. The embryos pro- 

 bably escape, as in most other Actiniae, through the mouth of the mother and 



