THE STAEFISH SOLASTEE ENDECA. 5 



The occurrence of muscle-fibres in the inner layer of the gonad-wall seems not 

 to be usual, or at least not to be generally recognized. Ludwig (13, p. 599) and 

 Delage (5, pp. 62-63) speak as if the layer in question consisted entirely of fibrous 

 connective tissue. In the case of Asferias vulgaris. Field (7, p. 106) states that the 

 muscular fibres of the egg-tube walls run in various directions, the outer and inner 

 fibres being at right angles to one another. He makes no mention of spaces between 

 the layers, nor are such spaces indicated in his illustration. 



In Starfish anatomy it seems to be the rule that in hollow structures with muscular 

 walls the longitudinal fibres lie internal to the circular ones, as, for example, in the 

 walls of the tube-feet and of the disc itself, as well as in the peristome and the 

 oesophagus and stomach. JVote. — In this connection attention may be called to the 

 statement in Bronn's ' Klassen ' (13, p. 580), that in the oesophagus the circular layer is 

 internal to the longitudinal one. This appears to be an error, as it is also said that 

 these layers are the continuations of corresponding layers in the peristome, and the 

 relative position of the circular and longitudinal muscles is correctly given on the 

 page before. 



The statement made above, to the effect that in Solaster endeca the spaces between 

 the inner and outer layers of the egg-tube wall are continuous with the genital sinus, 

 was based on a careful examination of serial sections through four gonads in an adult 

 Solaster of large size, and I have not the slightest doubt as to its correctness for this 

 particular species. 



In Ludwig's view the spaces in question are lacunar in character (13, pp. 599 Sc 

 613), being terminal expansions of the hsemal vessels within the genital sinuses. 

 Hamann, quoted in Ludwig (13, p. 599), described the spaces as having an endothelium- 

 like lining and as communicating both with the genital sinuses and with the cavities 

 of the hsemal tissue. 



According to Cuenot (3, p. 88) the spaces in question belong to the perihaemal 

 sinus system, while the cavities of the haemal vessels lead directly into the interior of 

 the egg-tubes. Macbride (15, p. 377, fig. 122) showed that in Asterina the spaces 

 between the inner and outer layers of the gonad-walls arise as expansions at the ends 

 of the genital branches of the aboral perihsemal sinus, but apparently in later develop- 

 meiit these spaces become completely shut off, owing to the formation of the septum 

 through which the growing egg-ducts burrow their way to the outside. However, 

 the same author (16, p. 449) describes the genital bra,nches of the aboral sinus as 

 swelling out at their blind ends so as to enclose the gonad cell-masses. 



In my series of sections referred to above a distinct cellular lining was present 

 in the larger spaces occurring around the roots and proximal parts of the egg- 

 tubes, but further along the tubes it became less definite and finally ceased to be 

 recognizable. 



