852 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The author's concluding observations on alternation of generation 

 are illustrated by diagrams, which explain his views ; the correspon- 

 dence between some llydromedusse and insects, where again we find a 

 long-living and feeding larva, and a short-lived sexual form, is ad- 

 verted to. Among the former there are (1) Trachymedusre, in which 

 all nutrition is effected during the medusoid stage; (2) Tubularia and 

 others, in which food is taken in during both hydroid and medusoid 

 conditions ; and (3) those — as Eucopella — in which nutrition is effected 

 only while the form is hydroid. 



New Medusae from the Red Sea.* — C. Keller commences with an 

 account of a new genus and species, Gastroblasta timida, a small Cras- 

 pcdote form, which was found for a few days only during the month 

 of March. The gastric cavity is a short tube with thick walls, well 

 provided with muscles ; at its base it is produced into four or more 

 processes which receive the radial vessels. At first each medusa has 

 only one central gastric tube, but in older forms there is more than 

 one ; the author was first inclined to think that he had to do with a 

 pathological phenomenon, but he soon found that the process was quite 

 normal and constant. The secondary gastric tubes form at first 

 siuuslike enlargements on the lower part of a radial vessel, and pro- 

 ject into the umbrellar cavity. Later on, this widens at its base, and 

 becomes perforated at its tip. This phenomenon is to be explained as 

 either due to an incomplete division of the Medusa, or as a lateral 

 gemmation. The former view is to be rejected, inasmuch as the 

 secondary gastric tubes arise without any division of the primary 

 stomach, and are at first without any oral orifice ; nor have fissive 

 processes of the disk ever yet been observed. We have, therefore, to 

 accept the second explanation, and to regard the gemmation as an 

 incomplete process, which has been profoundly modified by 

 cenogeny. 



Eeference to the observations of Hackel, and an enumeration of 

 observed cases of variability in the number of imjjortant organs afford 

 sufficient support to the position that gemmation is far from being 

 unknown among the Medusas. 



Keller finds it necessary to form a new fiimily of Gastroblastidae, 

 which he defines. 



The other new form now described is Cassiopea polypiides n. sp. ; 

 of this five difierently coloured varieties were observed. Among the 

 points studied were the characters of the yellow cells, which the author 

 examined with the view of deciding on their vegetable or animal 

 nature. The following are the results : treatment with iodine indi- 

 cated the presence of starch, but was not sufficient to establish the 

 vegetable character of the cells ; no blue coloration of the cell- 

 membrane was observable after treatment with iodine and sulphuric 

 acid ; but, as this reaction is not always to be depended on, Schulze's 

 reagent was tried, and resulted in the complete destruction of the 

 cells ; as the membranes were in time acted on by a dilute solution, 

 the result would appear to be that we have here to do, not with cell- 



* Zeitschr. f. Wiss. Zool., xxxviii. (1883) pp. 621-70 (3 pis.). 



