A NUMBER of professors stood behind their lecterns for their first classes of the semester last week and told the students gathered before them to get lost. "Please don't take this course," implored Alan Brinkley, the Dunwalke Associate Professor of History, as he stared at an auditorium where the class filled the aisles and spilled onto the stage. Other instructors who faced unworkable crowds excluded pass-fail students from enrolling in their courses.

The most notorious confusion of all surrounded a Core course called Literature and Arts B-16, "Abstraction in Modern Art." Like a horde of wildcatters racing to the site of a gusher, some 600 students (roughly a tenth of the undergraduate population) descended upon the Fogg Norton Lecture Hall, hoping for a spot in the survey course.

That was about twice the size the instructor, Associate Professor of Fine Arts Diane W. Upright, had in mind, and she told freshmen and sophomores in the class to make themselves scarce. Enter the Core's administrators, who told Upright she could only thin out her ranks by means of a random lottery.

So at the next class, students from all four years were invited to cast their lot (although an unidentified anarchist posted fliers in the classroom repeating Upright's original ban on youngsters) and 380 lucky gamblers are now enrolled in the course.

Clearly, the College's system of guessing course turnout each term and then scrambling to adjust for any errors has all the clarity and precision of a Jackson Pollack canvas. In a great many courses each term, either the classrooms or the teaching staffs prove too small to accommodate the students who show up for the first lectures. The result is by now a biennial ritual: the helter-skelter of relocations and the anxiety of lotteries.

On the other hand, as administrators have sensibly pointed out, the current early-semester confusion is far preferable to pre-registration. The right to shop around from class to class before choosing courses is a luxury well worth a couple of weeks of chaos each term.

But why doesn't the College require undergraduates to turn in non-binding study cards at the end of each preceding term? (Freshman could submit their fall-term cards over the summer.) That measure would not eliminate the rushing around that currently prevails, but it would certainly cut it down: administrators would not be off by hundreds when they schedule classrooms, and students would have an early indication of which courses are going to require lotteries. Standing Room Only is a sign that belongs outside a theater, not a classroom.