610 SUMMARY OP CURRENT RESEARCHES RELATING TO 



are sharply marked off from one another ; a cilium could not be 

 detected ; but in close connection with the cell there was found the 

 cell-layer which invests the afferent canals. This does not differ 

 essentially from the superficial investing layer, and it is only in the 

 finest terminal canals that the cells diminish in height. The endo- 

 derm, just as in Halisarca lohularis and Plahina, has the whole of its 

 wall lined by the collar-cells, although these are excessively small. 

 In the mesoderm we can distinguish hyaline and opaque substances, 

 the difference between which does not merely depend on the presence 

 of ciliated chambers in the latter, as much as on the possession by 

 the hyaline substance of small, highly refractive granules. The 

 siliceous bodies are found in the mesoderm alone, but they vary very 

 much in the extent to which they are developed. The author thinks 

 that he has been able to make out a pretty continuous series between 

 the normal quadriradiate forms and the complex candelabra which 

 distinguish this species, and he works out some points in their 

 homological relations. In an example from Cebu, Schulze found, at 

 some slight distance from the surface, a very small, and apparently 

 lately formed, siliceous spicule, imbedded in a round pigmented cell. 

 This observation leads him to believe that the spicule was really 

 developed within the mesoderm, and to give in his adhesion to the 

 doctrine of various spongiologists that the rudiments of the spicules 

 arise in cells. G. candelabrum is hermaphrodite, and though this has 

 afforded good opportunity for study, the author has not been able to 

 make out any definite arrangement or grouping of the genital 

 products. The sperm-spheres do not appear to differ essentially from 

 those found in other sponges. The ova are irregularly rounded and 

 so richly filled with yolk-granules as to completely obscure the pretty 

 large nucleus and nucleolus. Cleavage appears to be complete, and 

 the blastula, when formed, exhibits a single layer of delicate cylindrical 

 cells. 



Sexual Characters of Halisarca lohularis.* — Dr. M. Braun, in 

 reference to the statement of F. E. Schulze that this sponge is 

 dioecious, and the contrary opinions of Eimer, Haeckel, and others 

 that it is hermaphrodite, states that he has found by sections that the 

 specimens he examined at Trieste had the sexes united. At the same 

 time, the author is not of opinion that Schulze was not justified in 

 his conclusion ; he thinks it possible that, in this very low class of 

 animals, the sexual conditions of a species may not be yet fixed. In 

 Tuhularia mesemhrijanthemum, no doubt, hermaphrodite and dioecious 

 arrangements are respectively to be observed at different periods of 

 the year. Schulze says of H. lohularis that the sperm is produced 

 from the middle of July to the beginning of August, and ova from 

 the end of July to the beginning of September ; the sperm are, there- 

 fore, produced earlier than the ova. Cases of this kind are, as the 

 writer very justly observes, of the greatest importance in the study 

 of the difficult question of the differentiation of the sexes. 



* Zool. Anzcig, iv. (1881) pp. 232-4. 



