SCYPHOMEDUSAE 343 



small specimens with a low flat cup-shaped umbrella (Vanhoeffen, 1892, pi. ii, fig. i) 

 are put together with very large specimens of ± 200 mm. diameter with broad dome- 

 shaped umbrella (Brandt, 1838, pi. xxix; Mayer, 1906, pi. ii, fig. 6). Only P . hyacin- 

 thina is distinctly described with slender and high umbrella. The discrimination 

 of large dodecabostrycha and regina appears to be very arbitrary. 



/ believe that we here have to do only zvith a single species (to be called by the oldest 

 name hyacinthina) which appears in three different main types: forma dodecabostrycha, 

 forma hyacinthina typica and forma regina — a distinction similar to that given by Mayer 

 (19 10) but in another sense. The main types are connected by transitory stages, and the 

 characteristics overlap so that it is often very difficult to say to which form a given 

 species belongs.^ In the present series I distinguish besides the three principal types a 

 young developmental stage, preceding the dodecabostrycha stage, which I call the 

 "Bigelow" stage (here included in the dodecabostrycha group), transitional stages be- 

 tween forma dodecabostrycha and hyacinthina and intermediate stages between forma 

 hyacinthina and regifia. The distinction of these five stages seems to be supported by 

 the geographical and bathymetrical distribution. Whether they are biological or geo- 

 graphical races will be discussed later on (p. 362). 



I recognize the following five stages : 



(i) Forma dodecabostrycha. 



(a) Bigelow stage, as figured by Bigelow, 1909, pi. ix, fig. 2, described on p. 27 and 

 called by him '' dodecabostrycha-stage of P. hyacinthi?ta ", 5-17 mm. diameter. The 

 figure shows the restriction of endodermic pigment to the central stomach and the 

 rhopalia. The peripheral system is entirely hyaline; the rhopalia as a rule are pig- 

 mented. The ring muscle is already well developed, as are the pedalia, and the ring 

 furrow is deeply marked ; there is no apical projection of the stomach into the 

 mesogloea (no " Stielcanal"). 



(b) Dodecabostrycha typica. Small, up to 30-35 mm. diam., broader than high, 

 flat, cone-shaped, mostly with " Stielcanal " (apical projection of the stomach into 

 the mesogloea) ; gonads if present distinctly visible from the outside, pigment on 

 the stomach and ring sinus, peripheral zone transparent. See for instance Van- 

 hoeffen, 1892, pi. ii, fig. I, and pi. i, fig. i, non hyacinthina \; further, Maas, 1904, 

 pi. V, fig. 36 ; but not Brandt's (1838) type specimen of Chrysaora (Dodecabostrycha) 

 diibia, pis. xxix, xxx (see below under regina). 



(2) Transitional stages between forma dodecabostrycha and forma hyacin- 

 thina. 



Slender, as broad as high or a little higher than broad, from 35 mm. diam. 

 upwards ; pedalia and lappets slender, furrows between the pedalia reaching as far 

 as the coronal furrow and forming here a wavy line on its under border ; stomach 

 highly vaulted, often pointed, mostly without " Stielcanal ", mostly without or only 



1 The difficulties in discriminating the specimens evidently prove, I believe, that we really have to do with 

 only one large species. 



