148 ACTINLE OF ALBATR0S8 EXPLORATIONS l\r'MUl?KICn. 



ectodermal uiuscles of the teutaoles and disk form a simple l;iyer, the 

 mesoglo'a. not beinji^ raised into snpi)ortin«;" ])ro('e8ses. 



The stomato(henm is eh)ngiit('d, but witliout well-mai la'd siplmiio- 

 jilyi)hes. Its ec'to(b*rniaI lininj;' is thrown into very pronouniu'd fohls, 

 supported by delicate tiionuh hiuli h)n<iittnlinal ridi^es of n.ieso.u'hea 

 (PI. XXI, Fig. ID). 



The mesenteries are irregnhir in inunber. In siMtions of three speci- 

 mens, for example, there were respectively US, 3.*>, and .Ul ])airs. As a 

 rule a perfect and an imperfect jtair alternate, bnt this arrangement is 

 not infre(iuently intennpted by the succession <»f two j)airs of [>erfect 

 ones, or of three or two pairs ot' iin|>erfect ones. There are two pairs of 

 directive mesenteries, and the number of mesenteries intervening be- 

 tween them on each side is usually the sanu'. though tlu'ie are excep- 

 tions to this rule. In the specinn'u of which a sectitui is tiguredou PI. 

 XXI, Fig. 1!>, it will be seen that only eleven i)airs of mesenteries inter- 

 vene between the two directi\'es ( />) on one side, while there are as 

 many as twenty-one on the other side. This section represents the con- 

 dition as seen towards the level of the lower extremity of the stomato- 

 daMim. Higher n^) two pairs of nu'seiiteries are to be fiMind which are 

 not rci)resented at the level ligurcd, antl these increase tJie number of 

 mesenterial pairs of one side of the body to fourteen — ?*. c, thirteen 

 ])airs intervene bet ween the two directives, f^ven in the up|>ermost 

 si'ctions, however, there is not eqindity in the nund)er o\' the mesente- 

 ries of either side. That the irregularity which is tbund in the succes- 

 sion of |)erfect ami imperfect mesenteries is not an artilicial pioduction 

 is shown by the relation of the perfect i>airs on either side of the two 

 {x) and three (//) imperfect pairs of the ligiire. It is there seen that 

 these i)erfect pairs are attached tt) t he stomatoda-um opposite succes- 

 sive mesogheal ridges, and this rehition of the ridges to the insertion 

 of mesenteries, though not ctmstant, is of sutticient IVeipu'uce to Avar- 

 rant the assumption tlnit the groups of mesenteries .r. // are truly im- 

 perfect. 



The inesoglu>a of the mesenteries is considerably thicker a sht>rt dis- 

 tance from their insertion into the column wall than elsewhere and is 

 raised into only very low muscle processes. Consequently the muscle 

 pennons are almost wanting, the longitudinal nuiscles forming little 

 more than a simple layer over the surface of the mesoglcea. Kone of 

 the specimens examined were mature; imnmture ova were observed, 

 how«'ver, in the endoderm of some<tf the peit'ect nieseiit erics and in that 

 of the directives. 



The habits of this Ibnn suggested identity with that described l>y Ver- 

 rill ('S.'>) as Sa<i(irfii( spotKi'icoIa. Fxaniination o\' specimens of the 

 latter showed at once that the two forms were \ cry ditferent, *S'. spoiig- 

 ic<)l((, for example, possessing strong muscle pennons on the mesenteries 

 attached by a slight pedicle in a manner recalling the conditions de- 

 scribed by llertwig ("SiJ) for Lvioival'm n\j))q)1ia'a. 



