63<± SQMMARY OF CURRENT RESEARCHES RELATING TO 



the base of the funnel and there ends in a certain number of vacuoles ; 

 the author has convinced himself that these remarkable structures 

 are an integral part of the animal, but he is not able to make any 

 generalizations with regard to tbem. 



In the highest Siphonophora the mesoderm is represented by the 

 widening out of the lamella, at certain points, into a well-developed 

 gelatinous layer. 



While in the lowest, the Calycophorida, an air-sac is absent, it 

 only becomes more complicated as the organization of the Siphono- 

 phore becomes higher ; in these, however, it is still lined by ectoderm, 

 and never becomes, as Gegenbaur supposed, completely closed. Some 

 of the cells of the ectoderm are of very large size ; only one or two 

 cells forming csecal processes 2 mm. long ; the cells themselves may 

 be 1 or 1J mm. long, and their oval nuclei measure '13-15 mm., 

 so that they are among the very largest known in animal tissues. 



Development of Tubularia cristata. * — The development of 

 Tubularian Hydroids has been a subject of some dispute. The latest 

 paper, that of Ciamician, j describes an irregular segmentation 

 resulting in an epibolic gastrula. This result, so out of accord with 

 the development of other Hydroids, has been much questioned and 

 denied, and H. W. Conn has accordingly made a careful study of the 

 Tubularian embryo, in the case of T. cristata, avoiding the sources of 

 error in Ciamician's observations by removing the egg completely 

 from the medusa and examining it by itself. In the result he finds 

 that the development of T. cristata agrees completely with other 

 Hydroids, the segmentation and formation of the germinal layers 

 coinciding completely with Coelenterates in. general. Tubularia, 

 which has been considered somewhat of an anomaly in Hydroid 

 development, presents, therefore, no noteworthy difference from the 

 rest of the Hydroids. 



American Acalephse4 — J. W. Fewkes is adding considerably to 

 our knowledge of these forms. In discussing the characters of the 

 Ctenophore Ocyroe crystallina, the author points out that, according 

 to the classification of Chun, in which the Ctenophora are divided 

 into the Tentaculata and the Nuda, the form in question would be 

 placed with the non-tentaculate JBeroe, with which it has few other 

 anatomical likenesses. If Chun's classification is to be followed 

 Ocyroe must be regarded as a form connecting his two groups, and 

 indeed it has, as A. Agassiz has pointed out, " structural characters 

 of the Lobatse, Saccatae, and Eurystomaa." 



After describing Cassiopeia frondosa, the author comes to Linerges 

 rnercurius, which appears to be very abundant in the Gulf off the 

 Florida Keys ; one of its most interesting characters appears to be the 

 characters of the " hood " of the prominent otocyst ; when this latter 

 is looked at from above it resembles a spherical sac, in the centre of 

 which a single otolith may be seen, seated on a short peduncle ; the 



* Zool. Anzeig., v. (1882) pp. 483-4. 



t Zeitschr. f. wiss. Zool., xxxii. 



% Bull. Mus. Oomp. Zool. Cambridge, ix. pp. 251-310 (10 pis.). 



