51 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tinguished by the ringing of the skin, the pedicellate hydrotheoe, and 
the non-re tractile polyp, which is relatively much larger than the polyp 
of Halecium. 
Porifera. 
Nucleus of Sponges.* — M. J. Chatin recommends the Sponges, and 
especially the Calcareous forms, as very suitable objects fur the study of 
the nucleus. Little preparation is necessary, as fixation by 33 per cent, 
alcohol and staining with methyl-green or picrocarmine will generally be 
found sufficient ; where a more rigorous investigation is intended abso- 
lute alcohol is a good fixative. The mesodermal elements are the best to 
study, and especially those near the ectoderm. 
The nucleus varies a great deal in form, and is at times ramified ; the 
nuclear membrane is often clearly visible, for the cellular protoplasm is 
almost always clear and free from granules. The contained plasma has 
in it nuclein arranged in filaments which are aggregated towards the 
edges of the nucleus, or in similarly situated nucleoli. 
M. Chatin points out that the form of the nucleus of Sponges is 
very similar to that of the nucleus of Protozoa — a fact, he thinks, of 
considerable interest in zoological histology, when we reflect on the 
relationship between Sponges and Protozoa which has been sometimes 
insisted on. 
Protozoa. 
Psycho-physiological Studies on Protists. t — Dr. M. Yerworn has 
made an interesting series of investigations on the movements, reactions, 
and general behaviour of Protists. He began by studying the sponta- 
neous movements of uninjured Bacteria, Diatoms, Bhizopods, Flagellata, 
and especially ciliate Infusorians. Then he investigated their behaviour 
in relation to various stimuli — luminous, thermal, electrical, chemical, 
and mechanical. He made a great number of experiments with excised 
portions of Bhizopods and Ciliata, studying their movements and their 
reactions. Finally he watched the normal life, the food-seeking, house- 
making, pairing of Protozoa. 
He allows that the first impression of many Protists is that they 
possess many of the mental qualities of higher animals, for their move- 
ments often suggest sensation and deliberation. Further study does not 
corroborate this impression ; his own conclusion is that u all their move- 
ments are expressions of unconscious psychical processes.” Their 
structure is not such that there can be any centralized consciousness ; 
the characteristic movements are retained by little excised fragments ; 
the nucleus is certainly not a psychical centre. “ There is no alternative 
but to identify the psychical processes in the Protist organism with the 
molecular processes therein, and to seek their fundamental conditions in 
the qualities of the molecules.” Whether Dr. Yerwom’s conclusions 
are right or not, the abundant facts which he describes are most 
interesting. 
• Comptes Bendas, cxi. (1890) pp. 889-90. 
t • Pay cho- Physiology sche Protisten-Studien. Experimentelle Untersuchungen,’ 
Svo. Jena, 1889, viii. and 219 pp., 6 pis. and 27 figs. 
