842 



SCIENCE 



[K. S. Vol. XXXVII. No. 961 



eggs cleaved very slowly without fertilization. 

 The older observations of Thuret and of 

 Crouan that the eggs of Cutleria develop with- 

 out fertilization have been confirmed by 

 Church, who reports that on the English coast 

 Cutleria mulUfida develops mostly partheno- 

 genetically, female plants being hard to find 

 in August, and that scarcely any occur in tlie 

 latter part of the season, the eggs developing 

 without fertilization. As was previously ob- 

 served by Thuret and Bornet, Williams has 

 more recently found that the unfertilized eggs 

 of Dictyota and of Haliseris segment a few 

 times and then die. 



It is evident that the Phffiophyceae show a 

 strong tendency toward parthenogenetic de- 

 velopment and that natural parthenogenesis 

 may play an important part in the life history 

 of several species. None of the Fucacea, 

 however, have been reported as being able to 

 develop without fertilization, although Thuret 

 mentions that unfertilized eggs of Fucus kept 

 for several days become pear-shaped and that 

 a cellulose wall is sometimes present. Thuret's 

 observations have not been supported by 

 Farmer and Williams, who have never been 

 able to observe cellulose walls around unfer- 

 tilized eggs. My own observations are in har- 

 mony with those of Farmer and Williams. 

 While working at the Marine Bioogical Labo- 

 ratory at Woods Hole, the past summer, it 

 seemed worth while to apply to Fucus eggs 

 some of the well-known experimental methods 

 used by Loeb, Winkler, Delage, Lillie and 

 others, whereby unfertilized eggs of certain in- 

 vertebrates have been made to segment under 

 the influence of artificial physical and chemical 

 stimuli. 



Fucus vesiculosus, a dioecious species, oc- 

 curs near the shores between tide marks at 

 Woods Hole, and plants, both in the vegetative 

 and reproductive conditions, are usually 

 abundant. The spermatozoids and oospheres 

 are usually discharged sparingly during ebb 

 tide and abundantly during flood tide. Plants 

 were collected during ebb tide, the distal por- 

 tions removed and placed in dishes on ice over 

 night. Care was taken that the conceptacles 



bearing eggs and sperms were kept separate. 

 When it was desired to obtain the eggs and 

 sperms, dishes containing conceptacles were 

 filled with fresh sea-water, or after first ex- 

 posing the conceptacles to a hypotonic sea- 

 water, when eggs and sperms were discharged 

 in large numbers. The freshly extruded eggs 

 drop to the bottom of the dishes and can be 

 taken up with a pipette and transferred to 

 watch glasses for experiment. After a short 

 time the eggs show a tendency to adhere very 

 firmly to the bottom of the watch glasses so 

 that fluids can easily be poured off and others 

 added without losing the eggs. 



The process of fertilization in Fucus has 

 often been studied, and the details of develop- 

 ment were especially studied by Thuret and 

 later by Oltmanns. If the mature eggs and 

 sperms are mixed together in the same dish in 

 sea-water, the sperms collect in great num- 

 bers about the egg, and attaching themselves 

 to the periphery cause the eggs to rotate 

 rapidly by lashing the water with the cilia. 

 Soon the eggs lose the power of attracting the 

 sperms. They cease their rotation and settle 

 down. Such eggs are fertilized. Farmer and 

 Williams have shown that within five minutes 

 after mixing the sexual cells the sperms have 

 entered many eggs and within ten minutes the 

 sexual nuclei fuse. Soon after fertilization a 

 delicate membrane or cell wall is formed about 

 the periphery of the oospore. As noted by 

 Farmer and Williams, the character of the 

 cytoplasm changes markedly, tending to as- 

 sume a definitely radiating character, the lines 

 radiating from the nucleus as a center. The 

 oospores rest for about twenty-four hours, 

 during which time there is a rapid increase in 

 the thickness of the cell-wall and a further 

 change occurs in the structure of the cyto- 

 plasm like those described by Farmer and 

 Williams. At the periphery of the fertilized 

 egg, just below the wall, the cytoplasm shows 

 a definite alveolar structure. 



After some time many of the oospores as- 

 sume a pear-shaped form and by the next day 

 all have divided. The first division, as has 

 been observed by Eosenvinge and others, is at 



