DEPARTMENT OF MARINE BIOLOGY. 215 



eupyrene spermatozoa in great numbers, while around the fringes of the 

 agglutinations are active apyrene spermatozoa. Although the latter often 

 seem to be heaped up about an agglutinated mass and appear to be actively 

 pressing against it, this is not thought to be a chemotropism, since sometimes 

 an apyrene spermatozoon is seen moving directly away from the vicinity of 

 such a mass. On the other hand, it is believed that the massing of the apyrene 

 spermatozoa is due to the fact that they have been activated and to the 

 peculiar manner in which they move. It has been repeatedly observed that an 

 apyrene spermatozoon, once having started in a certain direction, alwaj^s 

 maintains it, unless one of the undulating membranes is stronger than the 

 other, when it will tend to travel in a circle. This last, however, is a condition 

 which only occasionally obtains. When an apyrene spermatozoon meets an 

 object it does not avoid it in the least, but merely pushes against it all the 

 harder. If it overcomes the obstacle it continues its way in the same direction 

 as before, but if it fails to get by it stays there, continually pushing against the 

 object. 



The conditions which obtain in a culture after the first hour are maintained 

 with but little change for several hours, there being a slight and gradual 

 increase in the size and number of agglutinations formed, but always there are 

 great numbers of active eupyrene spermatozoa above these masses. Finally, 

 however, the activity of the free eupyrene and of the apyrene spermatozoa 

 gradually slows down and then ceases, the duration of the culture depending 

 entirely upon the care with which it is maintained. In hanging-drop cultures 

 which were sealed with vasehne this condition of balance has been maintained 

 for as long as 72 hours, in fact until bacterial action put an end to it.^ 



The question naturally arises, does the activity of the apyrene spermatozoa 

 tend to prevent further agglutination of the eupyrene spermatozoa? The 

 writer is not in a position to answer this question directly, but one or two 

 conclusions may be pointed out which seem to be fully justified. The aggluti- 

 nation of the eupyrene spermatozoa is undoubtedly caused by a substance 

 given off by themselves as a result of their activities. The formation of the 

 two dense bars parallel to the two free edges and then their meeting to form 

 a dense area of eupyrene spermatozoa across the middle of the culture shows 

 that this substance raises the surface tension. That this substance is alkaline 

 in its nature is indicated by certain experiments in which a drop of a N/100 

 NaOH solution was introduced beneath the cover by means of a capillary 

 pipette at a time when the agglutinations were beginning to form. This had 

 the effect of causing an intense stimulation of short duration of the eupyrene 

 spermatozoa in the immediate neighborhood of the drop; this was followed 

 by their agglutination. The effect upon the apyrene spermatozoa was to 

 increase their activity. From the constant occurrence of the resumption of 

 activity by the apyrene spermatozoa around agglutinations of eupyrene sper- 

 matozoa, it seems evident that the substance which causes the latter stimu- 

 lates the apyrene spermatozoa to activity. 



There is considerable evidence which indicates that the two kinds of sperma- 

 tozoa of Stromhus together show the properties of facultative anaerobes, and 

 also, as far as it has been tested, that the things which stimulate the one kind 

 of spermatozoon inhibits the activity of the other, and vice versa. It has 

 been stated already that in cultures started in C02-charged sea- water, from 

 which the bubbles have ceased to arise, the activity of the eupyrene sperma- 

 tozoa is greatly inhibited, while the apyrene spermatozoa are altogether 

 stopped, except at the free edges of the culture, where they come into contact 



•Carnegie Institution of Washington Year Book No. 12, p. 178, 1913. 



