222 



SCIENCE. 



[N. S. Vol. VII. No. 164. 



It is well known that some one-celled 

 animals form ' filose pseudopodia,' that is, 

 temporary, fine threads of flowing sensitive 

 protoplasm. These serve for locomotion, 

 taking-in of food, tactile organ, etc., i. e. , 

 for relation with environment. 



A recent statement that the cells and 

 polar bodies in sea-urchin and starfish eggs 

 put forth similar threads and so establish 

 amongst themselves temporary living con- 

 nections led the speaker to examine other 

 animals. Filose phenomena were seen in 

 the living eggs of an Annelid, a Gasteropod 

 and a Lamellibranch, while preserved verte- 

 brate material indicated their presence there 

 also. 



In the large Nemertian worm, Cerebratu- 

 lus lacteus Verrill, the filose activities of the 

 polar bodies are less difficult to see than 

 those described in Echinoderms, and differ 

 characteristically from them. Diagrams 

 made from a series of camera drawings cov- 

 ering several hours' continuous observation 

 showed that the polar bodies are very 

 active in change of shape and in filose pro- 

 trusions. 



Each polar body has its special habit of 

 action. In each there is a progressive 

 specialization of activity. The polar bodies 

 look not unlike Eadiolarians, and when 

 the second becomes of a spindle shape, with 

 stars of filaments at its poles, it suggests 

 the amphiaster stage in karyokinetic cell- 

 division. This resemblance, so far as the 

 star-like groups of filaments are concerned, 

 is not superficial, if we accept* the statement 

 that the astral rays in the starfish egg are 

 often delicate, filose extensions of the con- 

 tractile protoplasm between vesicles of an 

 emulsion that makes up the egg ; for then 

 the internal stars and external stars are both 

 expressions of the same contractile power 

 and filose habit of protoplasm. Thus the 

 filose powers of protoplasm are shown to 



* The Living Substance : As Such and as Organ- 

 ism. G. F. Andrews. Ginn & Co. 1897. 



us through various strise, filaments, rays 

 and threads within cells, as well as through 

 those hitherto unsuspected, delicate, flow- 

 ing, thread-like, pseudopodial extensions 

 external to, and amongst, the cells of Met- 

 azoan masses. 



Tlie Effect of Salt Solutions on Unfertilized 



Eggs of Arbaeia. T. H. Morgan. 



If unfertilized eggs of Arbaeia are put 

 into sea water, to which 1.5 per cent, so- 

 dium chloride has been added and left there 

 from one to three hours, they will, when re- 

 turned to ordinary sea water, begin to seg- 

 ment after about half an hour. The divis- 

 ion is sometimes into two parts, oftener 

 into more than two parts, and does not in 

 any way resemble the normal cleavage. 

 These eggs continue to divide for at least 

 twelve hours, but do not develop into 

 embryos. 



Sections show that the female pronucleus . 

 persists in the egg in the salt solution 

 from two to four hours. After that time 

 the nuclear wall disappears and the chromo- 

 somes are set free in the cytoplasm, usu- 

 ally in the form of a dense cluster. During 

 the time that the eggs are in the salt solu- 

 tion the artificial astrospheres that have 

 been described for fertilized eggs appear. 

 When the eggs were returned to ordinary 

 sea water the chromosomes separate and 

 probably divide. The rays of the artificial 

 astrospheres that come in contact with 

 the chromosomes thicken and become less 

 granular. The chromosomes now begin 

 to migrate towards the centers of the sur- 

 rounding astrospheres. Later the chromo- 

 somes form resting nuclei, two or more. 

 Around these nuclei as centers the proto- 

 plasm begins to constrict, forming the 

 cleavage spheres seen from the surface. 

 Half an hour later the nuclei again resolve 

 themselves into chromosomes and a new 

 division, etc., succeed. 



The artificial astrospheres slowly fade 



