HYDROZOA CRASPEDOTA. 753 



mouth and near the aboral pole two short tentacles. The young animal 

 adheres by its proboscis to the margin of the bell of its host. It then 

 migrates into the cavity of the bell and affixes itself by its tentacles, two 

 new tentacles appearing between the two first formed, whilst the oral end 

 of the body elongates remarkably, and may be inserted into the mouth of 

 the T^irritopsis. At the same time it developes as many as six to seven 

 buds at its aboral pole which become larvae similar to their parent, and are 

 detached. The ridge, from which the peripheral part of the bell is formed, 

 appears in the same zone as the bases of the tentacles, the number of which 

 is increased by the development of four more. The ridge grows out at its 

 summit into intertentacular lobes, each of which bears a tentaculocyst. The 

 larval Medusa is now set free. The oral proboscis shortens, the stomach 

 pouches acquire their adult character, and the generative rudiments are 

 formed. A somewhat similar larva has been observed in the bell of Rhopa- 

 lonema velatum. (2) Cunina proboscidea (= C. vitred). In this species, in 

 C. rubiginosa s. rhododactyla, and apparently in C. (Cunoctantha) Kollikeri> 

 an asexual reproduction or sporogony occurs in both males and females, 

 which has been accurately worked out in the first-named of the three. 

 Immature sexual cells with a granular protoplasm wander from the sexual 

 organs into adjacent parts. They multiply by fission. Eventually one 

 cell ingulfs another, and the ingulfed cell divides and forms a morula. If 

 the inclosing cell lies in the endoderm of a festoon canal further develop- 

 ment of the inclosed cell into a ciliated lens-like body with ecto- and endo- 

 derm takes place. It escapes from the supporting cell, and is eventually 

 converted into a Medusa. During its growth it developes buds at the 

 aboral pole, one after another in C. proboscidea, which are detached, but may 

 remain in connection with a stolo prolifer in C. rubiginosa. Gemmation 

 does not appear to take place in C. Kollikeri. In the two last named the 

 Medusa becomes a true Cunanthid though differing in the number of its 

 segments from its parent, e. g. C. Kollikeri is eight-rayed, its young twelve. 

 In C. proboscidea the young sexually mature Medusa differs entirely from 

 its parent 1 . (3) Cunina (Cunoctantha) par asitica. The life-history of this 

 form is only partially known but is probably connected with a sporogony. 

 It is parasitic in Geryonia proboscidialis s. Carmarina fungiformis 2 . The 

 youngest stage observed consists of a colossal cell with pseudopodia adherent 

 to the bell-margin of the host, and partially inclosing a morula composed 

 of a cap of ciliated ectoderm cells and an irregular mass of entoderm cells. 



1 See Metschnikoff, Embryologische Studien an Medusen, Wien, 1886, pp. 119, 120. 



2 A sporogenetic brood seems to be capable of wandering. Metschnikoff states (op. cit. p. 122) 

 that he has found embryoes and buds of Cunina rubiginosa (rhododaclyla} in Polyxenia (Solmissus) 

 albescens. Hence the budding larvae found in various Geryonids may belong to an identical 

 species. 



The nomenclature of the Gcryonidae appears to be in much confusion. The two specific names 

 given in the text are used by Metschnikoff for the same medusa. 



3C 



