210 THE AUSTRALIAN HYDROMEDUS^, 



According to Metschnikoff (1) some of these, which possess no 

 thread-cells have also the function of devouring the trophosomes 

 of the colony when they get sick. With great acuteness Metsch- 

 nikoff (I.e.) follows up the similarity between this process and the 

 action of amoeboid wandering cells or white blood corpuscles and 

 festering cells, which perform the same duties in higher animals. 

 By the action of these analogous oi'gaus similar work is performed. 



These Machapolypes appear in three different forms which are 

 sometimes met with in the same colony. They may possess thread- 

 cells or adhesive cells, similar to those found in the Ctenophorse, 

 or both. I have described the Morphology and Physiology of 

 these Machopolypes elsewhere. (2.) 



An intermediate stage between the members of this latter 

 group and the Clavidae, is met with in Eudendrium, where there 

 are Blastostyles and Polypes, but Avhereboth may contain ripe ova, 

 and where the Polypes which mature the generative elements 

 afterwards, in many cases lose their tentacles, and so become 

 Blastostyles as it were under the eyes of the observer. 



I propose to place all Hyclroids mentioned above with the 

 exception of those which produce free Medusae, or which are 

 descended from Hydromedusge which once produced free Zooids, 

 in the first Suborder the Hydropolypinae. The great difficulty 

 in executing this task and classifying the Hydroniedusae accoi'ding 

 to whether their Gonophores are medusoid or not, lies in the great 

 similai-ity between Polypostyles, that is Gonophores derived from 

 a generative Polype direct, and Medusoid Gonophores, that is 

 rudimentary Medusae. 



I have attempted a classification, comprising all the Hydro- 

 medusa? in the Zoologischer Anzeiger, (3) but I fear, as I pointed 



(1.) E. Metschnikoff. Ueber die intracellulare Verdaming bei wirbellosen 

 Thieren. Arbeiten aus dem Zool. Inst, der Universitat Wien Band V. 

 (Translated into English, Quarterly Journal of Mik. Science, Nr. 93.) 



(2.) R. von Lendenfeld. Ueber Wehrthiere und Nesselzellen. Zeitschrift 

 fur wiss. Zool. Band, XXXVIII Seite, 355 (Translated into English 

 Annales and Magazine of Natural History, 5th Series. Nr. 71.) 



(3.) B. von Lendenfeld. Das System der Hydromedusen. Zoologischer 

 Anzeiger 18S4. 



