SCYPHOMEDUSAE 337 



collecting having been done almost exclusively far from shore. The only pelagic form 

 found by previous expeditions in the Antarctic Ocean and not collected by the 

 ' Discovery' is Diphilmaris antarctica, Maas, known from Cape Adare, Kaiser Wilhelm II 

 Land, and Anvers Island in the Palmer Archipelago. 



The occurrence of Tomoya haplonema in the waters off Cape Lopez, French Congo, 

 is interesting, the known distribution of this medusa having previously been restricted 

 to the Atlantic coasts of North and South America and the West Indies. 



Periphylla hyacinthina. All the 103 specimens have been referred to one single species. 

 It appears in three different main types, formerly believed to be three different species, 

 but actually nothing more than different stages of growth of a single species. I restrict 

 the name forma dodecabostrycha to small, flat specimens of 35 mm. maximum diameter, 

 mostly with gonads distinctly visible from without and with a " Stielcanal ". I unite all 

 large plump dome-shaped specimens, previously for the most part called dodeca- 

 bostrycha, with those determined as regma under the name forma regina. I reserve the 

 name forma hyocinthina (typica) for medium-sized slender specimens with pointed bell 

 and stomach. The small and feebly pigmented dodecabostrycha stages live generally in 

 more superficial layers ; they most probably have their origin on the continental slope, 

 and, slowly sinking into greater depths, are transformed into the hyacinthina and regina 

 stages. The larger darkly pigmented forms of hyacinthina (typica) and regina are true 

 bathypelagic forms and as a rule are caught far from the coast. 



Thus there exists a certain relation between the amount of pigmentation and the 

 depth in which the medusa lives, but there are also layers in which all stages of pig- 

 mentation and development occur together. 



There is an increase of size towards deep water, but not an increase of numbers with 

 depth as Broch states. 



Periphylla hyacinthina in the dodecabostrycha stage has not until now been found in 

 the tropics in superficial layers. In the present series there are several catches from 

 Ascension and the Gulf of Guinea, from 250-0 and 1 75-1 25-0 m. respectively. Their 

 occurrence is most probably due to cold upwelling currents. Some specimens of the 

 dodecabostrycha stage have been found in the Bellingshausen Sea and south of the South 

 Shetlands. This is very remarkable for similar young stages have never been found 

 before so far south in true Antarctic waters. The dodecabostrycha stage is preceded by a 

 rare young developmental stage, first described by Bigelow (1909), which I have called 

 the "Bigelow stage" in honour of the leading authority in medusology. This stage, of 

 which several specimens are present, is characterized by restriction of the dark endo- 

 dermic pigment to the central stomach and the rhopalia, the peripheral zone being 

 entirely hyaline. 



Atolla. I distinguish only two species of Atolla: wyvillei with smooth lappets, and 

 chuniw'ith lappets studded with tubercles. I divided the 185 specimens of A. wyvillei 

 in the present series into three groups or forms: zvyvillei (typica), bairdi and vernlli, 

 based on the characters of the furrows on the central disc. In the present series there 

 is not a single specimen with radial furrows running all over the disc. The gastro- 



