14 TIIÉEL, PRIAPULIDS AND SIPUNCULIDS OF THE SWEDISH ANTARCTIC EXPEDITION 1901 — 1903. 



As has been mentioned above, a larva of a shallow-water animal keeps in its 

 floating stage for a time ranging from a few days to two months, which certainly in 

 most cases is calculated too high. Supposing, too, that such a larva could sustain 

 a transport from polar-circle to polar-circle, that a direct under-current unites the 

 two circles in a straight line and that that current had a rapidity of the Florida stream 

 at its highest celerity — a thing which in fact is an impossibility — then it may be 

 very instructive to compute the time that would be required for a larva or another 

 object to traverse the space between the two polar-circles. 



According to Krummel, Walther and other distinguished scientific men, the 

 Florida stream runs at a råte of 1,50 to 2,50 m. per second. Presuming that a uniting 

 under-current such as we assume could have a rapidity of 2,50 m. per sacond — a 

 surface-current of the greatest rapidity in the world, or nearly so — how long would 

 it take for an object to be transported the long distance in question? 



The distance in a direct line from polar-circle to polar-circle is about 1,476 miles 

 (a swedish mile = 10 km.). Then the object in question goes 1,500 m. per minute, 

 90,000 m. per hour and 2,160,000 m. per day, that is to say in rourid numbers 22 miles 

 per day. In two months the larva has not been transported more than 1,320 miles. 

 Consequently, from these calculations we are entitled to draw the conclusion that 

 the larva is obliged to sink to the deep-bottom and to perish there before ha vin g 

 reached the opposite polar-circle. And yet we have calculated with something so 

 absurd as that an under-currents could run in a direct line from polar-circle to polar- 

 circle and with a rapadity of that of the Gulf-stream between Florida and the Ba- 

 hama Island at a time when it has its greatest velocity. 



In view of the above-mentioned reasoning, I may be allowed to put to every 

 scientist the question whether they really believe that a larva of such a limited 

 floating stage can endure the very long transport from polar-circle to polar-circle by 

 means of under- water currents? I think is most unlikely. 



Now we may pass över to the fifth point. In appreciating the phenomenon of 

 bipolarity, we have to take into consideration the very important fact, that many 

 marine animals are devoid of floating larval stages and develop in a more direct 

 manner, consequently that their young are totally independent of currents and in- 

 capable of removal in any noticeable sense. Such instances are met with especially 

 in the northern and southern regions. 



Leaving out the Sipunculids mentioned in this paper, some of them being per- 

 haps cosmopolitans, the Priapulids do certainly present a striking example of such 

 an instance. Though nothing is known of their embryology, I think that every na- 

 turalist, acquainted with this isolated genus, will agree with me in considering the 

 Priapulids to be devoid of the floating larval stages. Priapulus caudatus is found 

 in the Baltic sea, off the coasts of Denmark and all along the west coast of Scandi- 

 navia, off the coasts of Greenland, Spitzbergen etc. Notwithstanding this, a free 

 floating larva of it has never been observed. The same is the case with its nearest 

 relative, Hälicryptus spinosus, a relicta-form living only in the arctic and Baltic 

 seas. The latter is common in the archipelago of Stockholm, and for many years 



