28 



CTENOPHORA. 



It should still be mentioned, in connection with the gastrovascular system, that, according to Will ey 

 (p. 328), there is no excretory opening in Ctenoplana, while in Tjalfiella there is, at least, one. It wonld 

 not seem improbable, however, if further researches will prove such openings to exist also in Ctenoplana. 

 A great difference wonld appear to exist betwen Tjalfiella and Ctenoplana in regard to 

 the muscular system. Korotneff (p. 247) describes no less than three different muscular 

 systems in Ctenoplana: i. a dermal muscular system, 2. dorsoventral muscles and 3. a system of long- 

 itudinal muscles ("selbstandige Muskulatur der Ruderplattchen und Tentakeln"). The first of these 

 systems evidently corresponds to the usual Ctenophoran musculature, as appears from the description. 

 The dorsoventral muscles would appear to correspond, partly at least, to the radially arranged muscles 

 of other Ctenophores, though Willey may be partly right in maintaining (p. 328) that they are only 

 the dorsoventral trabeculse between the branches of the peripheral canals of the gastrovascular system. 

 (These trabeculse, however, will doubtless prove to contain muscles also). Much more remarkable is 

 the longitudinal muscular system, which would appear to be something otherwise quite unknown 

 among Ctenophores, as pointed out by Korotneff. There are two pairs of longitudinal muscles; 

 "jedes Paar korrespondiert mit seiner Seite und dient dazu die betreffenden Rippenplattchen in Bewe- 

 gung zu bringen, d. h. die letzten aus- und in die Taschen hineinzuziehen. Dabei aber verwachst 

 jedes Paar, bevor es sich an die Plattchentasche anheftet, zu einem gemeinsamen Muskelbtindel, 

 welcher im Querschnitte ein mondformiges Aussehen bekommt. Nach dem Anheften behalt der 

 Muskel dieselbe Form einige Zeit, um spater sich wieder zu theilen, bis an die folgende Plattchen- 

 tasche. In der Mitte zwischen zwei Taschen liegt jederseits ein Tentakel, dessen Muskulatur auch 

 von den Lansgmuskeln geliefert wird; dabei erfolgt dieselbe Verschmelzung von dem entsprechenden 

 Muskelpaar, wie es fur die Rippenplattchen soeben beschrieben ist". - - Similarly Willey writes: 

 "The muscles of the tentacles form part of the voluminous musculature, which, so far as I can make 

 out, affects the retraction of the aboral sense-organ and of the ctenophoral plates, which can be com- 

 pletely drawn into the body". "At a short distance on either side of the median stomachal plane the 

 sections in contracted specimens are almost entirely occupied by the convoluted bundles of muscles" 



(p. 328 29). From a closer inspection of the figures 

 of this muscular system given by Korotneff I 

 have become fully convinced that this remarkable, 

 complicated structure is nothing but the tentacle, 

 retracted and curled up within the tentacle 

 sheath. In the figure 3 of Korotneff reprod- 

 uced above (Fig. 3) a pair of such "muscles" are 

 Fig. 5. Section through the supposed "excretory canal" (Ex. k.) seen lying above the tentacle base, evidently within 



and "longitudinal muscles" (Lni.) of Ctenoplana. ., i t. ii i-n tt. 



heath ! Stl11 mOTe COnVlnCln g the 



*5is*~ 



>3kx3r^ 



^^ tt-g^--:::--' 1 '* 

 >x S^V--^^ 1 -i- -5- 



'^^y^*. 



> K ^T^iJT^^ss* 



(Aft,* Korotneff. Tat VIII. Fig. 4} 



Fig. 4 of Korotneff, reproduced in Fig. 5; it is 



quite beyond doubt that this figure represents a section of the tentacle curled up within the sheath, not 

 an excretory canal and longitudinal muscles as Korotneff thinks. - - That the "excretory canal" is 

 really the opening of the tentacle sheath was observed by Willey; as seen from the above quoted 

 passage he did not, however, understand the nature of the "longitudinal muscles", so that when 



