\ 4 Porifera. 



characterises Vie. Had the genus \_Ute\ not been already well established D. 

 would have hesitated in attributing generic importance to a character which is 

 found in so many very distinct sponges. In Synute we meet with a very unusual, 

 if not unparalleled condition, in the complete fusion of a large number of Syconoid 

 individuals to form a compact solid sponge invested in a common cortex. Utella 

 is Haeckel's Sycandra hystrix , with a cloacal cortex of longitudinal oxeotes 

 (fide H.). - - Leaving Sycyssa and Lelapia we come to two important forms derived 

 from Grantia through the disappearance of its tubar skeleton : in Anamixilla large 

 triradiate spicules , out of all proportion in size to the flagellate chambers, gene- 

 rally lie across them and replace the normal tubar skeleton of small elements ; in 

 Leucandra on the other hand the flagellate tubes themselves , by shortening and 

 multiplication , have lost all geometric regularity and the skeleton has suffered 

 corresponding changes. In many species of the last genus, e. g. L. aspera, the 

 canal-system is of the type characterising Lendeufeld's Sylleibidae ; D. does not 

 consider this a character of systematic value : in this genus also we reach the 

 climax of the Leuconoid canal-system. In Leucyssa D. has had the opportunity 

 of personally ascertaining that for L. incrustans the skeleton consists of a very 

 dense, irregular felt-work of spiuose oxea. - - With these Grantidae there is a 

 curious parallelism of genera in the Heteropidae, whose early separation from 

 the stem is shown by their system of subdermal sagittal triradiates. Grantessa 

 repeats the canal-system of Grantia, Heteropia shows a cortex of longitudinal 

 oxeotes like that of Ute , while the Sylleibid canal-system of Vosmaeropsis recalls 

 Leucandra aspera. The Amphoriscidae, with subdermal quadriradiates, 

 present a Syconoid canal-system in Heteropegma, Amphoriscus, and Syculmis while 

 Sylleibid or Leucouoid chambers place Leucilla on a level with Leucandra. - 

 Consideration of these families shows that the characteristic form of external pro- 

 tection has been developed while the canal -system was still Syconoid and 

 to remains to identify the race through subsequent modifications. Origin of 

 Heterocoela. Leucosolenia tripodifera [cf. Bericht f. 1891 Porif. p 8], with its 

 radiate branches and their inverted spiculation , shows the probable mode of pas- 

 sage from the Homocoela upwards. The existence of Lendenfeld's Homo- 

 dermidae and Leucopsidae cannot be accepted. 



