Both species (Figs. 11 and 12) have the same biogeographic distribution and the same preferences for physical conditions. Some plots are comparable even in their detailed structure. The morphology of both species is closely related and a
discrimination is often (Saito et al., 1981) or not at all possible until the terminal stage (Hemleben et al., 1989). They occur over a wide geographic range with a preference for low and mid latitudes and physical conditions in these
regions. The only distinct feature in their relation with the analysed physical parameters is their occurrence in areas with high temperatures at 200 m with distributions skewed towards higher temperatures. This relation suggests a deeper
water habitat of these species, however, G. siphonifera is common in the mixed layer, e.g in the Caribbean. Hilbrecht and Thierstein (1996) observed a benthic behaviour of G. siphonifera in cultures. The biology and ecologic preferences may,
therefore, not be understood from observations in the water column alone (see discussion section).